A co-processing system and method for casting and biomass charcoal production

Abstract

This invention discloses a co-processing system for casting and biomass charcoal production, comprising a combustion device. The inlet of the combustion device is connected to a casting waste gas source in the casting process, and the outlet of the combustion device is connected to a waste heat recovery and cascade utilization system. The waste heat recovery and cascade utilization system has multiple heating branches with different temperature grades, which are correspondingly connected to carbonization devices, casting auxiliary process equipment, and biomass charcoal production auxiliary process equipment with different heat requirements in the biomass charcoal production process. The outlet of the carbonization device is connected to the inlet of the combustion device. This invention achieves waste-to-waste treatment and cascade energy utilization, eliminating the need for RTO and activated carbon treatment, and has advantages such as low operating costs, high energy efficiency, and no secondary pollution.

Description

Technical Field

[0001] This invention relates to the field of flue gas treatment technology, specifically to a co-processing system and method for casting and biomass charcoal production. Background Technology

[0002] Lost foam casting, a type of casting, is a precision casting process that uses polystyrene (EPS) or polymethyl methacrylate (EPMMA) foam plastics to create patterns. During pouring, the patterns undergo pyrolysis and gasification under the action of high-temperature molten metal, producing a large amount of black smoke containing benzene compounds and aromatic organic pollutants (VOCs). This type of exhaust gas is characterized by high temperature, high dust content, and large fluctuations in organic matter concentration, making it difficult to treat.

[0003] Currently, mainstream technologies for treating foundry waste gas include regenerative thermal oxidizers (RTO), activated carbon adsorption, and catalytic combustion. While RTO can achieve efficient VOCs decomposition, it requires significant investment and high energy consumption. Activated carbon adsorption, on the other hand, suffers from secondary hazardous waste generation after adsorption saturation and high disposal costs. How to achieve clean treatment of lost foam casting waste gas while remaining economically feasible remains a pressing challenge for the industry.

[0004] On the other hand, biomass carbonization (such as charcoal production from straw, nutshells, and wood chips) has developed rapidly in recent years as a renewable energy utilization method. However, the carbonization process itself consumes a large amount of heat energy (usually requiring a pyrolysis temperature of 400-900℃) and produces carbonization waste gas containing combustible components such as CO, H2, and CH4.

[0005] There is currently a lack of effective technical solutions to complement and match the "waste gas treatment needs" and "thermal energy needs" of the two processes, so that the oxidation heat of the waste gas in the casting process can provide a heat source for the carbonization process, while the carbonization waste gas can be returned to the furnace for incineration to achieve self-sustaining combustion, forming a synergistic system of waste treatment and energy cascade utilization. Summary of the Invention

[0006] This invention aims to solve the technical problems of high energy consumption and serious secondary pollution in existing foundry waste gas treatment, as well as the high cost of biomass carbonization process due to reliance on external heat sources. It provides a synergistic treatment system and method that deeply couples foundry and biomass carbonization.

[0007] To solve the above-mentioned technical problems, the present invention adopts the following solution: A co-processing system for casting and biomass charcoal production includes a combustion device. The inlet of the combustion device is connected to a casting waste gas source in the casting process, and the outlet of the combustion device is connected to a waste heat recovery and cascade utilization system. The heat output end of the waste heat recovery and cascade utilization system is connected to the inlet of a carbonization device in the biomass charcoal production process, and the outlet of the carbonization device is connected to the inlet of the combustion device.

[0008] Preferably, the device also includes a heat treatment apparatus for activating biochar or heat treatment of castings. The inlet of the heat treatment apparatus is connected to the outlet of the combustion apparatus, and the heat output of the heat treatment apparatus is connected to the inlet of the waste heat recovery and cascade utilization system.

[0009] Preferably, the combustion device is a two-chamber combustion device, the carbonization device is a carbonization furnace, and the heat treatment device is a heat treatment furnace, wherein: The air inlet of the secondary combustion chamber is connected to the casting exhaust gas source and the combustible flue gas outlet of the carbonization furnace, respectively, for mixing and burning the VOCs exhaust gas generated by casting and the combustible exhaust gas generated by the carbonization furnace. Carbonization furnaces are used for the carbonization of biomass raw materials; Heat treatment furnaces are used for the activation reaction of biochar or the heat treatment of castings; The heat output end of the waste heat recovery and cascade utilization system includes at least three heating branches with different temperature grades, wherein: The first heating branch is connected to the heat input end of the heat treatment furnace; The second heating branch is connected to the heat input end of the carbonization furnace; The third heating branch is connected to the casting auxiliary process equipment; It also includes a flue gas recirculation system. The inlet of the flue gas recirculation system is connected to the combustible flue gas outlet of the carbonization furnace, and its outlet is connected to the air inlet of the secondary combustion chamber. It is used to transport the combustible waste gas generated by the carbonization furnace back to the secondary combustion chamber to participate in combustion.

[0010] Preferably, the waste heat recovery and cascade utilization system includes: The flue gas direct branch has its inlet connected to the flue gas outlet of the secondary combustion chamber and its outlet connected to the heat input end of the heat treatment furnace, thus forming the first heating branch. And those connected in series according to the direction of flue gas flow: The first heat exchanger has its hot-side inlet connected to the flue gas outlet of the heat treatment furnace, and its cold-side medium outlet forming the second heating branch, which is connected to the heat input end of the carbonization furnace. The second heat exchanger has its hot-side inlet connected to the hot-side outlet of the first heat exchanger, and its cold-side medium outlet forms the third heating branch. The third heat exchanger has its hot-side inlet connected to the hot-side outlet of the second heat exchanger, and its cold-side medium outlet forms a fourth heating branch.

[0011] Preferably, the third heating branch is connected to the casting preheating chamber and / or the hot sand lifting device; the fourth heating branch is connected to the coating drying chamber and / or the branch drying and crushing machine in the casting process.

[0012] Preferably, the secondary combustion chamber is equipped with a burner, and its furnace design temperature is 850-1100℃, with a flue gas residence time of ≥2 seconds.

[0013] Preferably, the carbonization furnace is a continuous external heating rotary kiln or a vertical fixed bed carbonization furnace.

[0014] Preferably, the heat treatment furnace is an intermittent or continuous heat treatment furnace.

[0015] Preferably, the bottom of the secondary combustion chamber is provided with an ash collection hopper; the pipelines included in the flue gas recirculation system are provided with flame arresters and regulating valves.

[0016] This invention also provides a method for the co-processing of casting and biomass charcoal production based on the above system, comprising the following steps: Step 1: Collect the VOCs waste gas generated in the casting process and send it to the combustion device; at the same time, pressurize the combustible waste gas generated in the carbonization process of the carbonization device and send it to the combustion device. Step 2: The mixed exhaust gas in the combustion device is fully combusted, so that VOCs are completely decomposed; Step 3: The clean flue gas produced by combustion enters the waste heat recovery and cascade utilization system, and after cascade heat exchange, it generates multiple heat media of different temperature grades. Step 4: The heat medium generated after the cascade heat exchange is respectively transported to the carbonization unit, casting auxiliary process equipment and biomass charcoal production auxiliary process equipment; Step 5: Emission of exhaust gas after cascade utilization; The combustible waste gas generated by the carbonization device is continuously returned to the combustion device through the flue gas return system, forming a closed-loop energy cycle.

[0017] Preferably, when the system includes a heat treatment device, in step three, the clean flue gas generated by combustion is first transported to the heat treatment device for the activation reaction of biochar or the heat treatment of castings. The flue gas after passing through the heat treatment device then enters the waste heat recovery and cascade utilization system for cascade heat exchange.

[0018] Preferably, the cascade heat exchange process includes: the flue gas generated by the heat treatment device first flows through the first heat exchanger, and after heat exchange, a heat medium of 400-900℃ is generated for use in the carbonization furnace; then it flows through the second heat exchanger, and after heat exchange, a heat medium of 200-400℃ is generated; finally, it flows through the third heat exchanger, and after heat exchange, a heat medium of 60-150℃ is generated.

[0019] Preferably, the combustion process uses foundry waste gas and combustible waste gas from the carbonization furnace as the main fuel sources; the combustible waste gas generated by the carbonization furnace is continuously returned to the secondary combustion chamber through the flue gas recirculation system, forming a closed-loop energy cycle.

[0020] The beneficial effects of this invention are as follows: 1. The system is highly coupled and uses waste to treat waste. Specifically, it uses VOCs waste gas generated during the lost foam casting process as fuel and carbonization waste gas as supplementary fuel, and achieves co-destruction in the secondary combustion chamber. There is no need to purchase additional fuels such as natural gas, which greatly reduces operating costs.

[0021] 2. This system utilizes waste heat in a cascade manner to maximize energy efficiency. Based on the principle of temperature matching, high-temperature heat is used in heat treatment furnaces and secondary high-temperature heat is used in carbonization furnaces, medium-temperature heat is used for casting preheating, and low-temperature heat is used for drying, achieving energy grade matching. The comprehensive thermal efficiency can reach over 85%. Grade is a professional term borrowed from the field of thermal energy engineering, referring to the "quality of energy" or "level of energy," specifically the temperature.

[0022] 3. The system simplifies end-of-pipe treatment and eliminates secondary pollution. After multi-stage heat exchange, the exhaust gas temperature is low and pollutants are completely decomposed. There is no need for RTO and activated carbon, thus completely eliminating the problem of hazardous waste disposal of activated carbon.

[0023] 4. The system can achieve closed-loop energy circulation and self-sustaining operation. The carbonization waste gas continuously flows back to the secondary combustion chamber to participate in combustion, forming a closed-loop energy circulation. The system can achieve self-sustaining operation and only requires a very small amount of fuel replenishment.

[0024] 5. Using waste heat to preheat castings and hot sand can reduce casting defects; using waste heat to dry coatings can shorten the production cycle; using waste heat for biomass charcoal heat treatment can improve the quality of charcoal products. Attached Figure Description

[0025] Figure 1 This is a system process flow diagram of the present invention.

[0026] Explanation of markings in the diagram: 1-Foundry exhaust gas source; 2-Secondary combustion chamber; 3-Carbonization furnace; 4-Heat treatment furnace; 5-First heat exchanger; 6-Second heat exchanger; 7-Third heat exchanger; 8-Paint drying chamber; 9-Tree drying and crushing machine; 10-Regulating valve; 11-Casting preheating chamber; 12-Hot sand lifting device; 13-Fan; 14-Chimney; 15-Flame arrester. Detailed Implementation

[0027] The present invention will be further described in detail below with reference to the embodiments and accompanying drawings, but the embodiments of the present invention are not limited thereto.

[0028] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "longitudinal," "lateral," "horizontal," "inner," "outer," "front," "rear," "top," and "bottom," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of this invention is in use. 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 limitations on this invention.

[0029] In the description of this invention, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set up," "have," "install," "connect," and "connect" 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; and they can refer to the internal communication between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0030] Example 1 like Figure 1 As shown, this embodiment provides a co-processing system for casting and biomass charcoal production, including a combustion device, a carbonization device, a waste heat recovery and cascade utilization system, and a flue gas recirculation system.

[0031] The combustion device employs a secondary combustion chamber 2, whose inlet is connected to the casting waste gas source 1 in the casting process to receive VOCs waste gas generated during casting. The secondary combustion chamber 2 houses a burner with a furnace design temperature of 850-1200℃ and a flue gas residence time of ≥2 seconds to ensure complete decomposition of VOCs. An ash collection hopper is located at the bottom of the secondary combustion chamber 2; its position and structure are standard technology for existing secondary combustion chambers 2, used to collect particulate matter generated during combustion.

[0032] The carbonization unit uses carbonization furnace 3 for the carbonization of biomass raw materials. Carbonization furnace 3 is a continuous externally heated rotary kiln that receives heat from the waste heat recovery system to maintain a carbonization temperature of 400-600℃ (for example, in the preparation of ordinary biochar) or 400-900℃ (for example, in the preparation of high-quality carbon-based materials). The combustible flue gas outlet of carbonization furnace 3 is connected to the air inlet of the secondary combustion chamber 2 through a flue gas recirculation system.

[0033] The flue gas recirculation system includes a recirculation pipeline connecting the combustible flue gas outlet of the carbonization furnace 3 and the air inlet of the secondary combustion chamber 2. Along the flue gas recirculation direction, the pipeline is sequentially equipped with a flame arrester 15, a regulating valve 10, and a blower 13. The flame arrester 15 prevents flame backflow into the secondary combustion chamber 2; the regulating valve 10 controls the recirculation flow rate; and the blower 13 pressurizes the carbonization waste gas and sends it into the secondary combustion chamber 2. The outer wall of the pipeline is equipped with a heat tracing cable and an insulation layer to prevent tar condensation. The pipeline is laid at a 2-5° inclination towards the carbonization furnace 3, and a drain outlet is generally located at the lowest point. The sequence is as follows: carbonization furnace 3, flame arrester 15, regulating valve 10, blower 13, secondary combustion chamber 2.

[0034] The inlet of the waste heat recovery and cascade utilization system is connected to the flue gas outlet of the secondary combustion chamber 2, and its heat output end includes multiple heating branches with different temperature grades. In this embodiment, the waste heat recovery system includes a first heat exchanger 5, a second heat exchanger 6, and a third heat exchanger 7 connected in series according to the flue gas flow direction.

[0035] The hot side inlet of the first heat exchanger 5 is directly connected to the flue gas outlet of the second combustion chamber 2 (since no heat treatment furnace is provided in this embodiment), and its cold side medium outlet forms the first heating branch, which is connected to the carbonization furnace 3 of the carbonization furnace 3 to provide a high-temperature heat source of 400-900℃.

[0036] The hot-side inlet of the second heat exchanger 6 is connected to the hot-side outlet of the first heat exchanger 5, and its cold-side medium outlet forms a second heating branch, which is connected to the casting auxiliary process equipment. In this embodiment, the second heating branch is connected to the casting preheating chamber 11 and the hot sand lifting device 12, providing a medium-temperature heat source of 200-400℃ for preheating the medium-frequency furnace body, preheating the castings, and heating the hot sand.

[0037] The hot-side inlet of the third heat exchanger 7 is connected to the hot-side outlet of the second heat exchanger 6, and its cold-side medium outlet forms a third heating branch, which is connected to the auxiliary process equipment for biomass charcoal production. In this embodiment, the third heating branch is connected to the branch drying and pulverizing machine 9, providing a low-temperature heat source of 60-150℃ for drying and pulverizing biomass raw materials (branches).

[0038] The hot-side outlet of the third heat exchanger 7 is connected to the chimney 14. The exhaust gas after cascade utilization is discharged through the chimney 14 in compliance with standards. An online flue gas monitoring probe is installed inside the chimney 14.

[0039] The workflow of this embodiment is as follows: Step 1: The VOCs waste gas generated during casting is collected and sent to the secondary combustion chamber 2; at the same time, the combustible waste gas generated during the carbonization process of the carbonization furnace 3 is pressurized by the fan 13 of the flue gas recirculation system and sent to the secondary combustion chamber 2 through the flame arrester 15 and the regulating valve 10.

[0040] Step 2: The mixed exhaust gas in the secondary combustion chamber 2 is fully combusted at a high temperature of (850-1200℃) for 2.5 seconds, and VOCs and tar are completely decomposed into CO2 and H2O.

[0041] Step 3: The high-temperature clean flue gas generated by combustion enters the waste heat recovery system, flowing sequentially through the first heat exchanger 5, the second heat exchanger 6, and the third heat exchanger 7. After heat exchange in the first heat exchanger 5, a heat medium of about 400-900℃ is generated and transported to the carbonization furnace 3 to maintain the carbonization temperature of 400-900℃. After heat exchange, the second heat exchanger 6 generates a hot medium of about 200°C, which is then transported to the casting preheating chamber 11 and the hot sand lifting device 12. After heat exchange in the third heat exchanger 7, a heat medium of about 100°C is generated and transported to the branch drying and pulverizing machine 9.

[0042] Step 4: The exhaust gas after heat exchange in the third heat exchanger 7 is discharged through the chimney 14 in compliance with emission standards.

[0043] Throughout the process, the combustible waste gas generated by carbonization furnace 3 is continuously returned to the secondary combustion chamber 2 through the flue gas recirculation system, where it mixes and burns with the foundry waste gas, forming a closed-loop energy cycle. The system uses foundry waste gas and combustible waste gas from the carbonization furnace as the main fuel sources, requiring no external fuel.

[0044] In this embodiment, the combustible waste gas generated by carbonization furnace 4 mainly includes: Carbon monoxide (CO): One of the main gaseous products, it is flammable.

[0045] Hydrogen (H2): A combustible gas with a high calorific value, which is usually produced in large quantities at temperatures above 400°C.

[0046] Methane (CH4): An important combustible hydrocarbon gas and a major component of coke oven gas, etc.

[0047] Other hydrocarbons, including ethylene (C2H4) and ethane (C2H6), also have high calorific values. In the design of this embodiment, they are directly fed into the secondary combustion chamber at 850-1200°C via a flue gas recirculation system, perfectly addressing their dual properties. Utilizing its "fuel" properties, the combustible components in the secondary combustion chamber release heat during combustion, replacing some of the external fuel and achieving "waste treatment with waste".

[0048] Addressing its "polluting" properties: The high-temperature environment of the secondary combustion chamber can completely decompose tar and highly toxic VOCs and PAHs, converting them into harmless CO2 and H2O, thus avoiding complex tar separation and purification equipment.

[0049] Example 2 This embodiment adds a heat treatment device (heat treatment furnace or activation furnace) to the existing embodiment 1 for the activation reaction of biochar or the heat treatment of castings.

[0050] The heat treatment device in this embodiment uses a heat treatment furnace 4, which is an intermittent box furnace. Its heat input end is the heat exchange coil inside the furnace chamber, which is connected to the flue gas outlet of the secondary combustion chamber 2 through a flue gas direct branch to form the first heating branch (high temperature heating) and provide a high temperature heat source of about 1100°C.

[0051] The structure of the waste heat recovery and cascade utilization system has been adjusted as follows: Flue gas direct branch: The flue gas outlet of the secondary combustion chamber 2 is connected to the heat input end of the heat treatment furnace 4; First heat exchanger 5: The hot side inlet is connected to the flue gas outlet of the heat treatment furnace 4, and the cold side medium outlet forms the second heating branch, which is connected to the carbonization furnace 3. Second heat exchanger 6: The hot side inlet is connected to the hot side outlet of the first heat exchanger 5, and the cold side medium outlet forms a third heating branch, which is connected to the casting auxiliary process equipment. Third heat exchanger 7: The hot side inlet is connected to the hot side outlet of the second heat exchanger 6, and the cold side medium outlet forms the fourth heating branch, which is connected to the biomass charcoal auxiliary process equipment. The workflow of this embodiment is as follows: Step 1: The VOCs waste gas generated during casting is collected and sent to the secondary combustion chamber 2; at the same time, the combustible waste gas generated during the carbonization process of the carbonization furnace 3 is sent to the secondary combustion chamber 2 through the flue gas recirculation system.

[0052] Step 2: The mixed exhaust gas in the secondary combustion chamber 2 is fully combusted at a high temperature of 850-1200℃, and VOCs are completely decomposed.

[0053] Step 3: The high-temperature clean flue gas produced by combustion is divided into two paths: The first high-temperature flue gas is directly transported to heat treatment furnace 4 through the flue gas direct branch for the activation reaction of biochar or heat treatment of castings. The second stream of high-temperature flue gas serves as the main loop of the heat circulation network, entering the subsequent cascade utilization system.

[0054] Step 4: The flue gas after being used in the heat treatment furnace 4 enters the first heat exchanger 5. After heat exchange, a secondary high temperature (400-900℃) heat medium is generated. The heat medium is heat transfer oil or hot air, which is then transported to the carbonization furnace 3 to maintain the carbonization of biomass.

[0055] Step 5: The flue gas from the first heat exchanger 5 enters the second heat exchanger 6, and after heat exchange, a 200°C heat medium is generated. The heat medium is hot air or medium-temperature heat transfer oil, which is then transported to the casting preheating chamber 11 and the hot sand lifting device 12.

[0056] Step 6: The flue gas from the second heat exchanger 6 enters the third heat exchanger 7, and after heat exchange, a 100°C heat medium is generated. The heat medium is hot air or hot water, which is then transported to the paint drying chamber 8 and the branch drying and crushing machine 9.

[0057] Step 7: The exhaust gas after heat exchange in the third heat exchanger 7 is discharged through the chimney 14 in compliance with emission standards.

[0058] Throughout the process, the combustible waste gas generated by the carbonization furnace 3 continuously flows back to the secondary combustion chamber 2, forming a closed-loop energy cycle.

[0059] It should be noted that the secondary combustion chamber was originally standard equipment in the fields of waste incineration and hazardous waste treatment, used to perform secondary high-temperature incineration of unburned gases and organic matter produced by primary combustion, ensuring the complete decomposition of pollutants. Key features: Temperature: 850-1200℃ (sufficient to decompose all organic matter); Dwell time: ≥2 seconds (to ensure complete reaction); Turbulence: High (to ensure uniform mixing); Several reasons why a secondary combustion chamber is necessary: Reason 1: The VOCs generated by lost foam casting have a complex composition: benzene series compounds (benzene, toluene, ethylbenzene, xylene), polycyclic aromatic hydrocarbons (naphthalene, anthracene, phenanthrene, etc.), styrene monomers and polymers. Decomposition temperature requirements: Most organic compounds can decompose at a minimum of 750℃, while benzene series compounds and polycyclic aromatic hydrocarbons require a minimum of 850℃ for complete decomposition. Dioxins require a minimum of 850℃ and a residence time of ≥2 seconds for complete destruction. Ordinary combustion equipment (such as boilers and hot air furnaces) cannot guarantee this; the temperature is not high enough (usually 600-800℃), the residence time is not long enough (usually <1 second), and the mixing is not uniform enough. Only a secondary combustion chamber can guarantee 850-1100℃, ≥2 seconds, and sufficient turbulence to ensure the complete decomposition of VOCs into CO2 and H2O, without secondary pollution.

[0060] Reason 2: The combustible waste gas produced by the carbonization furnace consists of: CO (carbon monoxide 10-30%), H2 (hydrogen 5-20%), CH4 (methane 5-15%), and high concentration of tar (complex organic matter). Tar will condense and block the pipes at low temperatures (<800℃). Tar needs high temperatures to be completely decomposed (≥850℃). Ordinary burners cannot handle high tar waste gas.

[0061] Advantages of the secondary combustion chamber: instantaneous pyrolysis of tar at high temperatures of 850-1100℃, long residence time to ensure complete combustion, and direct introduction without pretreatment.

[0062] The calorific value of VOCs in lost foam casting is 3000-5000 kcal / m³, making it the primary fuel, while the calorific value of the exhaust gas from the carbonization furnace is 1500-2500 kcal / m³, serving as auxiliary fuel. The combined calorific value of these two exhaust gases is sufficient to sustain combustion in the secondary combustion chamber, requiring no external fuel (or only a small amount for ignition), thus achieving "waste treatment with waste." If the secondary combustion chamber is not used, the lost foam casting exhaust gas requires an RTO (energy-consuming process), and the carbonization furnace exhaust gas requires separate treatment (energy consumption), with each system consuming its own energy.

[0063] The flue gas temperature at the outlet of the secondary combustion chamber is 850-1100℃, which precisely meets the following requirements: Heat treatment furnace requirements: 850-1000℃ (highest grade); Carbonization furnace requirements: 400-900℃ (medium to high grade); Preheating requirement: 200-400℃ (medium grade); Drying requirements: 60-150℃ (low grade).

[0064] This solution uses a single unit to simultaneously perform VOCs decomposition, carbonization waste gas treatment, high-temperature heat source production, and particulate matter collection. If other equipment is used to replace the secondary combustion chamber, an RTO or catalytic combustion furnace (for VOCs treatment) would be required. Tar incinerator (to treat carbonization waste gas), hot air furnace or boiler (to generate a high-temperature heat source), and dust collector (to collect particulate matter). At least four pieces of equipment are required, significantly increasing investment and land occupation.

[0065] Example 3 This embodiment is basically the same as Embodiment 2, except that: the heat treatment furnace 4 uses two independent furnaces connected in parallel: one is a biochar activation furnace, dedicated to the activation treatment of biomass char; the other is a casting heat treatment furnace, dedicated to heat treatment processes such as annealing, normalizing, and quenching of castings. The heat input ends of both furnaces are connected to the flue gas outlet of the secondary combustion chamber 2 through a flue gas direct branch, which can allocate the high-temperature flue gas flow according to production needs. The carbonization furnace 3 is a vertical fixed-bed carbonization furnace, and the raw material is a mixture of rice husks and fruit shells. A tar separator is added to the flue gas recirculation system pipeline to further reduce the tar content and extend the service life of the pipeline.

[0066] In the waste heat recovery system, the cold side medium of the first heat exchanger 5 is heat transfer oil, which is supplied to the carbonization furnace 3 through the heat transfer oil circulation system; the cold side medium of the second heat exchanger 6 and the third heat exchanger 7 is air, which is directly transported to the hot spot through the hot air pipeline.

[0067] Example 4 This embodiment is basically the same as embodiment 1, except that the flue gas outlet of the heat treatment furnace 4 is also connected to the air inlet of the secondary combustion chamber 2 through a pipe. When the heat treatment furnace 4 generates combustible waste gas under specific process conditions, it can also be sent back to the secondary combustion chamber 2 to participate in combustion, further improving the flexibility and adaptability of the system.

[0068] Industrial Application Example: For instance, a lost foam casting company produces 5,000 tons of castings annually and simultaneously constructs a production line for 1,000 tons of biochar annually. After adopting the system of this invention: the exhaust volume of the lost foam casting line is 20,000 m³ / h, and the VOCs concentration is approximately 2,000 mg / m³; the carbonization furnace processes fruit tree branches as raw material, with a char yield of approximately 30%, and the calorific value of the carbonization waste gas is approximately 1,500 kcal / m³; the secondary combustion chamber is designed to have a temperature of 950℃ and a residence time of 2.5 s; after the carbonization waste gas is recycled, it can replace approximately 35% of the auxiliary fuel; the waste heat recovery system can recover approximately 2.5 × 10⁻⁶ heat annually. 6 The energy consumption is equivalent to saving approximately 300 tons of standard coal. Chimney emission tests show that particulate matter is less than 10 mg / m³, benzene compounds were not detected, and all indicators are better than the national emission standards. The annual savings are approximately 500,000 yuan in RTO operating costs, 300,000 yuan in activated carbon procurement and disposal costs, and 400,000 yuan in carbonization furnace fuel costs, resulting in a comprehensive annual economic benefit of approximately 1.2 million yuan.

[0069] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Based on the technical essence of the present invention, any simple modifications, equivalent substitutions, and improvements made to the above embodiments within the spirit and principles of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A co-processing system for casting and biomass charcoal production, characterized in that, It includes a combustion device, the inlet of which is connected to the casting waste gas source (1) in the casting process, the outlet of which is connected to the waste heat recovery and cascade utilization system, the heat output end of the waste heat recovery and cascade utilization system is connected to the inlet of the carbonization device in the biomass charcoal production process, and the outlet of the carbonization device is connected to the inlet of the combustion device.

2. The co-processing system for casting and biomass charcoal production according to claim 1, characterized in that, It also includes a heat treatment device, which is used for the activation reaction of biochar or the heat treatment of castings. The inlet end of the heat treatment device is connected to the outlet end of the combustion device, and the heat output end of the heat treatment device is connected to the inlet end of the waste heat recovery and cascade utilization system.

3. The co-processing system for casting and biomass charcoal production according to claim 2, characterized in that, The combustion device is a secondary combustion chamber (2), the carbonization device is a carbonization furnace (3), and the heat treatment device is a heat treatment furnace (4), wherein: The air inlet of the secondary combustion chamber (2) is connected to the combustible flue gas outlet of the casting waste gas source (1) and the carbonization furnace (3) respectively, for mixing and burning the VOCs waste gas generated by casting and the combustible waste gas generated by the carbonization furnace (3). The carbonization furnace (3) is used for the carbonization of biomass raw materials; Heat treatment furnace (4) is used for the activation reaction of biochar or heat treatment of castings; The heat output end of the waste heat recovery and cascade utilization system includes at least three heating branches with different temperature grades, wherein: The first heating branch is connected to the heat input end of the heat treatment furnace (4); The second heating branch is connected to the heat input end of the carbonization furnace (3); The third heating branch is connected to the casting auxiliary process equipment; It also includes a flue gas recirculation system. The inlet of the flue gas recirculation system is connected to the combustible flue gas outlet of the carbonization furnace (3), and its outlet is connected to the air inlet of the secondary combustion chamber (2). It is used to transport the combustible waste gas generated by the carbonization furnace (3) back to the secondary combustion chamber (2) to participate in combustion.

4. The co-processing system for casting and biomass charcoal production according to claim 3, characterized in that, The waste heat recovery and cascade utilization system includes: The flue gas direct branch has its inlet connected to the flue gas outlet of the secondary combustion chamber (2) and its outlet connected to the heat input end of the heat treatment furnace (4), thus forming the first heating branch. And those connected in series according to the direction of flue gas flow: The first heat exchanger (5) has its hot side inlet connected to the flue gas outlet of the heat treatment furnace (4), and its cold side medium outlet forms the second heating branch, which is connected to the heat input end of the carbonization furnace (3). The second heat exchanger (6) has its hot side inlet connected to the hot side outlet of the first heat exchanger (5), and its cold side medium outlet forms the third heating branch. The third heat exchanger (7) has its hot side inlet connected to the hot side outlet of the second heat exchanger (6), and its cold side medium outlet forms a fourth heating branch.

5. The co-processing system for casting and biomass charcoal production according to claim 4, characterized in that, The third heating branch is connected to the casting preheating chamber (11) and / or the hot sand lifting device (12); the fourth heating branch is connected to the coating drying chamber (8) of the casting process and / or the branch drying and crushing machine (9).

6. The co-processing system for casting and biomass charcoal production according to claim 3, characterized in that, The secondary combustion chamber (2) is equipped with a burner, and its furnace design temperature is 850-1200℃, with a flue gas residence time of ≥2 seconds.

7. The co-processing system for casting and biomass charcoal production according to claim 3, characterized in that, The carbonization furnace (3) is a continuous external heating rotary kiln or a vertical fixed bed carbonization furnace.

8. The co-processing system for casting and biomass charcoal production according to claim 3, characterized in that, The heat treatment furnace (4) is an intermittent or continuous heat treatment furnace.

9. The co-processing system for casting and biomass charcoal production according to claim 3, characterized in that, The bottom of the secondary combustion chamber (2) is provided with an ash collection hopper; the pipelines included in the flue gas recirculation system are provided with flame arresters (15) and regulating valves (10).

10. A method for the co-processing of casting and biomass charcoal production based on the system described in any one of claims 1-9, characterized in that, Includes the following steps: Step 1: Collect the VOCs waste gas generated in the casting process and send it to the combustion device; at the same time, pressurize the combustible waste gas generated in the carbonization process of the carbonization device and send it to the combustion device. Step 2: The mixed exhaust gas in the combustion device is fully combusted, so that VOCs are completely decomposed; Step 3: The clean flue gas produced by combustion enters the waste heat recovery and cascade utilization system, and after cascade heat exchange, it generates multiple heat media of different temperature grades. Step 4: The heat medium generated after the cascade heat exchange is respectively transported to the carbonization unit, casting auxiliary process equipment and biomass charcoal production auxiliary process equipment; Step 5: Emission of exhaust gas after cascade utilization; The combustible waste gas generated by the carbonization device is continuously returned to the combustion device through the flue gas return system, forming a closed-loop energy cycle.

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