Radioactive combustible solid waste treatment device and method

Abstract

The invention relates to a radioactive combustible solid waste treatment device and method. The device comprises a gasification furnace, an air mixing system, a flue gas recirculation system, a steam mixing system, a combustion furnace and a stored ash ashing device. Materials are subjected to various reactions in the gasification furnace to form gas products, liquid tar and solid residues (bottom ash), the gas products enter the combustion furnace to be fully combusted, in the process, flue gas mixed with water vapor is introduced into the gasification furnace from the position below a fire grate of the gasification furnace, a material layer and a pyrolysis gas layer through a flue gas recirculation system, and the gas products are fully combusted. The water vapor source comprises two parts, namely water vapor generated by combustion of pyrolysis gas in the combustion furnace and water vapor supplied from the outside. After the water vapor enters the cracking gasifier, the water vapor and coke are subjected to water gas reaction on a coke burning layer, so that the waste treatment effect is further improved; the cracking layer participates in the material cracking process, so that the cracking rate is increased, further cracking of macromolecular products is promoted, and generation of heavy tar is reduced.

Description

Technical Field

[0001] This invention relates to the field of radioactive waste treatment technology, specifically to a radioactive combustible solid waste treatment device and method. Background Technology

[0002] The nuclear industry generates a large amount of radioactive waste during operation and decommissioning, of which combustible solid waste accounts for a significant portion (approximately 50%), such as plastics, rubber, cotton textiles, wood, and resins. This waste requires inorganic and volume-reducing treatment before final disposal to save on disposal costs and improve the safety of long-term disposal. Incineration, as one of the earliest developed radioactive waste volume reduction technologies, can not only achieve significant volume reduction but also inorganic treatment, which is beneficial for final disposal. Therefore, radioactive combustible solid waste incineration technology is widely used in countries such as the United States, France, Germany, and Japan, becoming one of the main technologies for treating radioactive waste.

[0003] Currently, waste incineration technology has advanced to the most advanced pyrolysis incineration technology. Pyrolysis incineration refers to a stepwise pyrolysis-incineration process, where the pyrolysis process of waste and the combustion process of pyrolysis products are carried out separately. Taking the pyrolysis incineration technology developed by the China Institute of Radiation Protection as an example, the pyrolysis furnace is in an oxygen-deficient atmosphere. After the material is filled into the furnace, the material at the bottom undergoes an oxidation reaction with the air to form a stable char layer, while the material at the top undergoes a cracking reaction using the heat provided by the char layer. The gaseous products generated by cracking are premixed with a sufficient proportion of air and then enter the incineration chamber for oxygen-enriched combustion. This technology requires no external heating, has low energy consumption, produces less fly ash, is easier to purify, has a higher radionuclide retention rate, a higher waste volume reduction ratio, and can achieve good treatment results for combustible solid waste with a plastic content of 60% or less. Due to these advantages, this technology has become the most widely used radioactive combustible solid waste treatment technology in my country.

[0004] However, with the rapid development of the nuclear industry, the proportion of plastic polymer materials in radioactive combustible solid waste has increased significantly. Especially in radioactive combustible solid waste generated by nuclear power plants, its proportion has reached over 80%, exceeding the upper limit of existing pyrolysis incineration technology for accepting plastic waste. Therefore, a new waste treatment process is needed to effectively treat waste with high plastic content. Existing pyrolysis incineration technology has prominent problems in treating radioactive combustible solid waste with high plastic content. The reaction of the material in the pyrolysis furnace is mainly thermal decomposition under low-temperature conditions, and the products contain a large amount of tar. These tar substances coke in the pyrolysis furnace, forming slag, which interferes with the normal operation of the feeding and stirring systems. Furthermore, tar condensation can also lead to blockages in downstream pipelines and equipment corrosion, increasing the frequency of equipment maintenance and shortening the equipment's lifespan. In addition, due to the high calorific value of plastics, the equipment's heat load is high, forcing a reduction in waste treatment capacity.

[0005] Therefore, there is a need to develop a novel thermal volume reduction technology that can reduce the amount of tar generated during the pyrolysis of waste with high plastic content, effectively avoiding problems such as coking. To address the above technical issues, this patent designs a device and method for treating radioactive combustible solid waste. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a radioactive combustible solid waste treatment device and method, aiming to partially solve the aforementioned technical problems.

[0007] To achieve the above objectives, the present invention provides the following technical solution: On one hand, a radioactive combustible solid waste treatment device is proposed, comprising: a gasifier, a mixing system, a flue gas recirculation system, a steam mixing system, a combustion furnace, and an ash storage and ashing device; wherein, the gasifier includes a feeding mechanism, a pyrolysis gas reforming section, a material pyrolysis section, a first ignition system, a first thermocouple, a second thermocouple, a first pressure gauge, a second pressure gauge, and a primary air supply pipeline; the flue gas recirculation system includes a first branch, a second branch, a third branch, a first heating jacket, a heating jacket for the main flue gas recirculation pipeline, an induced draft fan, flue gas recirculation valves, a main flue gas recirculation pipeline, and valves, thermocouples, and flow meters for each branch; part of the flue gas generated by combustion is drawn back to the gasifier from the main flue gas outlet pipeline by the induced draft fan, and the recirculated flue gas... The total flow rate is controlled by the opening of the flue gas recirculation valve installed on the main circulation pipeline. The recirculated flue gas is heated by the heating jacket of the main circulation pipeline and enters the gasifier through the first branch, the second branch, and the third branch respectively. The first branch is equipped with a first heating jacket to reheat the flue gas flowing through the first branch. The steam mixing system includes a low-temperature steam inlet, a heating jacket, a first valve, and a mixing pipe. Liquid water is heated into low-temperature steam by a steam generator and enters the heating jacket from the low-temperature steam inlet. The heating jacket is located in the main flue gas outlet pipeline. The steam is indirectly heated by the waste heat of the flue gas in the heating jacket. The heated steam enters the main circulation pipeline through the mixing pipe. The steam mixing flow rate is controlled by the opening of the first valve.

[0008] As a preferred technical solution, the gasifier also includes an upper grate and a lower grate arranged vertically. The material is fed into the gasifier through a feeding mechanism and accumulates on the upper grate, forming a material layer to be burned in the material pyrolysis section. Air is introduced from the primary air supply pipe, and the first ignition system can ignite the material layer.

[0009] As a preferred technical solution, the material layer to be burned formed in the material pyrolysis section is divided into an ash layer, a coke layer and a pyrolysis layer from bottom to top, and steam is introduced into the gasifier from three positions: below the upper grate, in the middle of the material pyrolysis section and at the bottom of the pyrolysis gas reforming section.

[0010] As a preferred technical solution, the air mixing system includes: a pyrolysis gas pipeline, a secondary air pipeline, a secondary air flow meter, a second valve, a second heating jacket, and a third thermocouple; the pyrolysis gas flows out from the gasifier, passes through the pyrolysis gas pipeline, which is connected to the secondary air pipeline, the secondary air flow rate is controlled by the opening of the second valve and monitored by the secondary air flow meter, and the temperature is monitored by the third thermocouple; the secondary air is preheated by the second heating jacket before being mixed with the pyrolysis gas, and then mixed with the pyrolysis gas and enters the combustion furnace together.

[0011] As a preferred technical solution, the combustion furnace includes a second ignition system, a combustion chamber, a flue gas duct, a fourth thermocouple, a fifth thermocouple, a third pressure gauge, and a fourth pressure gauge; the pyrolysis gas mixed with air enters the combustion chamber and is ignited by the second ignition system; the flue gas generated by combustion can flow out from the flue gas duct and be discharged after passing through the downstream flue gas after-treatment stage.

[0012] As a preferred technical solution, the ash storage and ashing device includes an ash storage and ashing chamber, a microwave generating component, and a baffle plate. The solid residue (bottom ash) remaining after the gasification of the material in the gasifier is first discharged into the ash storage and ashing chamber for temporary storage. At the same time, the microwave generating component emits microwaves to heat the residual carbon in the bottom ash, so that it can react completely.

[0013] On the other hand, a method for treating radioactive combustible solid waste based on the above-mentioned radioactive combustible solid waste treatment device is proposed, the method comprising the following steps: Pre-processing materials: Pre-processing the materials to be processed by packaging them into pre-processing material packages; Preheating combustion furnace: Open the second valve, start the second heating jacket to preheat the secondary air, start the main induced draft fan at the tail end of the device, a negative pressure is formed in the system, and air enters the combustion furnace from the secondary air duct; start the second ignition system, inject diesel fuel into the combustion furnace from the second ignition system, the diesel fuel spray mixes with the air and is ignited by the spark plug of the ignition system; Start the gasifier: Turn on the primary air blower, open the valve of the primary air supply pipe, open the first baffle of the feeding mechanism, the material bag falls onto the second baffle of the feeding mechanism, close the first baffle, open the second baffle, the material bag falls onto the upper grate of the gasifier, close the second baffle; start the first ignition system, spray diesel fuel into the gasifier, the spark plug ignites the spray, the generated high-temperature flame ignites the lower layer of material, close the first ignition system; control the primary air flow by adjusting the valve opening of the primary air supply pipe until the material layer temperature can stably reach the preset combustion temperature. After the lower layer of material is stably burning, the heat released by combustion heats the upper layer of material, the upper layer of material undergoes oxygen-deficient pyrolysis, the generated pyrolysis gas flows into the pyrolysis gas pipe, and mixes with the preheated secondary air before entering the combustion furnace for combustion; Start the flue gas recirculation system: Open the flue gas recirculation valve, turn on the induced draft fan, and open the valves of the first branch, the second branch, and the third branch; turn on the first heating jacket and the heating jacket of the main flue gas recirculation pipeline; Start the steam mixing system: First, turn on the steam generator connected to the low-temperature steam inlet, and the steam generator will produce low-temperature steam of about 100 to 150 degrees Celsius. The low-temperature steam enters the heating jacket through the low-temperature steam inlet and is heated by the waste heat of the flue gas. After being heated by the waste heat, the steam enters the main flue gas circulation pipeline through the mixing pipe, mixes with the circulating flue gas, and flows together through each branch into the gasifier. Ash removal: The bottom ash falls into the ash storage and ashing chamber connected to the bottom of the gasifier under the action of gravity. At the same time, the microwave generating component emits microwaves into the ash storage and ashing chamber to heat the residual carbon in the bottom ash and make it continue to react into gaseous products. After the system has been running for a period of time, the bottom plate of the ash storage and ashing device is opened to discharge the bottom ash stored in the ash storage and ashing chamber.

[0014] As a preferred technical solution, the preheating combustion furnace specifically involves controlling the temperature in the combustion furnace to be heated to 600–1200 degrees Celsius.

[0015] As a preferred technical solution, the flue gas recirculation system is activated by controlling the temperature in the first branch to be 600-700 degrees Celsius, and controlling the temperature in the second and third branches to be in the range of 200-750 degrees Celsius.

[0016] As a preferred technical solution, when the generated cracked gas flows into the cracked gas pipeline and mixes with the preheated secondary air before entering the combustion furnace for combustion, the secondary air supply is adjusted by adjusting the opening of the second valve to regulate the combustion state of the cracked gas in the combustion furnace until the upper temperature of the combustion furnace stabilizes within 800 to 1200 degrees Celsius. This temperature is detected by the fourth thermocouple.

[0017] Compared with the prior art, the technical solution of this application has the following beneficial effects: The radioactive combustible solid waste treatment device proposed in this invention is the most core component of the radioactive combustible solid waste treatment system. This process combines anoxic self-sustaining pyrolysis, steam reforming, flue gas recirculation, and flue gas waste heat utilization.

[0018] Among them, the advantages of anoxic self-sustaining pyrolysis are good waste adaptability, extremely low energy consumption, and good volume reduction; the advantages of steam reforming are low tar production, thus it has a good effect on the treatment of waste with high plastic content, and it can promote the gasification of pyrolysis residue and reduce the ash loss on ignition rate.

[0019] The advantages of flue gas recirculation include the ability to utilize the heat in the flue gas to heat materials, and the fact that flue gas contains a large amount of carbon dioxide and water vapor, both of which are excellent gasifying agents that can effectively improve the pyrolysis process. The advantages of flue gas waste heat utilization include the effective use of waste heat to heat water vapor, saving energy and simultaneously achieving preliminary cooling of the flue gas.

[0020] In summary, the most prominent beneficial effect of the technology created by this invention is its good adaptability to radioactive combustible solid waste with high plastic content, and a significant reduction in the tar content of the product. At the same time, the technology created by this invention has low energy consumption and good economic efficiency. Attached Figure Description

[0021] Figure 1This is a simplified structural diagram of a radioactive combustible solid waste treatment device proposed in this invention; Figure 2 This is a simplified structural diagram of the ash storage and ashing device in a radioactive combustible solid waste treatment apparatus proposed in this invention; Figure 3 This is a simplified flowchart illustrating a method for treating radioactive combustible solid waste proposed in this invention. Figure 4 This is a schematic diagram of a method for treating radioactive combustible solid waste proposed in this invention.

[0022] Explanation of reference numerals in the attached drawings: Gasifier 1; Feeding mechanism 1-1; Pyrolysis gas reforming section 1-2; Material pyrolysis section 1-3; First ignition system 1-6; First thermocouple 1-7; Second thermocouple 1-8; First pressure gauge 1-9; Second pressure gauge 1-10; Primary air supply pipe 1-11; Upper grate 1-4; Lower grate 1-5; Mixing system 2; Pyrolysis gas pipe 2-1; Secondary air pipe 2-2; Secondary air flow meter 2-3; Second valve 2-4; Second heating jacket 2-5; Third thermocouple 2-6; Flue gas recirculation system 3; First branch 3-1; Second branch 3-2; 3-3 Third branch; 3-4 First heating jacket; 3-5 Main pipeline heating jacket; 3-6 Exhaust fan; 3-7 Flue gas circulation main pipeline; 3-8 Flue gas recirculation valve; 4 Steam mixing system; 4-1 Low temperature steam inlet; 4-2 Heating jacket; 4-3 First valve; 4-4 Mixing pipeline; 5 Combustion furnace; 5-1 Second ignition system; 5-2 Combustion chamber; 5-3 Flue gas pipeline; 5-4 Fourth thermocouple; 5-5 Fifth thermocouple; 5-6 Third pressure gauge; 5-7 Fourth pressure gauge; 6 Ash storage and ashing device; 6-1 Ash storage and ashing chamber; 6-2 Microwave generating component; 6-3 Insertion plate. Detailed Implementation

[0023] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0024] Please see Figure 1-2 The main functions of this device and method are: 1. The materials react in the gasifier, where the lower layer of material combusts with oxygen, and the heat released from the combustion heats the upper layer of material, causing it to undergo thermal decomposition. The reaction products are incineration ash and pyrolysis gas. The volume of the incineration ash is only a fraction of the original waste volume. The incineration ash is temporarily stored in an ash storage box below the gasifier. The pyrolysis gas is mixed with preheated air and then enters the combustion furnace, where it is fully combusted. The resulting flue gas flows out of the combustion furnace through the outlet.

[0025] 2. Simultaneously with material pyrolysis, flue gas mixed with water vapor is introduced into the gasifier through a flue gas recirculation system from below the gasifier grate, the material layer, and the pyrolysis gas layer. The water vapor comes from two sources: one is the water vapor generated by the combustion of pyrolysis gas in the combustion furnace, and the other is externally supplied water vapor. After entering the gasifier, the water vapor reacts with coke in the coke layer to form a water-gas reaction, further increasing the waste volume reduction ratio; in the pyrolysis layer, it participates in the material pyrolysis process, increasing the pyrolysis rate and promoting the further pyrolysis of large molecular products, reducing the formation of heavy tar; in the pyrolysis gas layer, it undergoes a reforming reaction with tar-like substances in the pyrolysis gas, promoting the further pyrolysis of tar into smaller molecular gases, thereby achieving the goal of reducing tar-like products. In addition, the bottom ash is discharged into an ash storage and ashing device installed at the bottom of the gasifier. This device temporarily stores the bottom ash while using microwave heating to perform secondary ashing of the residual carbon blocks in the bottom ash, thereby further reducing the loss on ignition of the bottom ash.

[0026] Example 1 Continue reading Figure 2 A radioactive combustible solid waste treatment device is proposed, comprising a gasifier 1, a mixing system 2, a flue gas recirculation system 3, a steam mixing system 4, and a combustion furnace 5.

[0027] The gasifier 1 includes a feeding mechanism 1-1, a pyrolysis gas reforming section 1-2, a material pyrolysis section 1-3, an upper grate 1-4, a lower grate 1-5, a first ignition system 1-6, a first thermocouple 1-7, a second thermocouple 1-8, a first pressure gauge 1-9, a second pressure gauge 1-10, and a primary air supply pipe 1-11. Material is fed into the gasifier through the feeding mechanism 1-1 and accumulates on the upper grate 1-4, forming a material layer of a certain thickness. At this time, air is introduced through the primary air supply pipe 1-11, and the material is ignited by the first ignition system 1-6. After the material is ignited, the first ignition system 1-6 stops working. The heat generated by the combustion layer heats the upper layer of material, causing thermal pyrolysis. The material is divided into three layers from bottom to top: an ash layer, a coke layer, and a pyrolysis layer. Water vapor is introduced from three locations: below the upper grate 1-4, in the middle of the material pyrolysis section 1-3, and at the bottom of the pyrolysis gas reforming section 1-2. It reacts with the residual coke, the material, and the pyrolysis gas, promoting complete gasification of the material and further breaking down large molecular products into smaller molecular gases. Finally, the ash is temporarily stored in the ash storage and ashing chamber 6-1, while the small molecular pyrolysis gas flows to the combustion furnace 5. During this process, the temperature of the pyrolysis gas at the top of the gasifier is monitored by the first thermocouple 1-7, the temperature of the material combustion layer is monitored by the second thermocouple 1-8, the pressure at the top of the gasifier is monitored by the first pressure gauge 1-9, and the pressure at the bottom of the furnace is monitored by the second pressure gauge 1-10.

[0028] The mixing system consists of a pyrolysis gas pipeline 2-1, a secondary air pipeline 2-2, a secondary air flow meter 2-3, a second valve 2-4, a second heating jacket 2-5, and a third thermocouple 2-6. The pyrolysis gas flows out from the gasifier, passes through the pyrolysis gas pipeline 2-1, and is connected to the secondary air pipeline 2-2. The secondary air flow rate is controlled by the opening of the second valve 2-4 and monitored by the secondary air flow meter 2-3. The temperature is monitored by the third thermocouple 2-6. Before mixing with the pyrolysis gas, the secondary air is preheated by the second heating jacket 2-5, and then mixed with the pyrolysis gas and enters the combustion furnace 5 together.

[0029] The flue gas recirculation system consists of a first branch 3-1, a second branch 3-2, a third branch 3-3, a first heating jacket 3-4 for a branch 3-3, a heating jacket 3-5 for the main flue gas recirculation pipeline, an induced draft fan 3-6, a flue gas recirculation valve 3-8, the main flue gas recirculation pipeline 3-8, and valves, thermocouples, and flow meters for each branch. Part of the flue gas generated during combustion is drawn back to the gasifier 1 from the main flue gas pipeline 5-3 by the induced draft fan 3-6; this is called flue gas recirculation. The total flow rate of the recirculated flue gas is controlled by the opening of the flue gas recirculation valve 3-8 installed on the main recirculation pipeline 3-7. The recirculated flue gas is first heated by the main pipeline heating jacket 3-5, and then enters the gasifier 1 through the first branch 3-1, the second branch 3-2, and the third branch 3-3 respectively. The first branch 3-1 is equipped with a first heating jacket 3-4 to reheat the flue gas flowing through it. The flue gas flow rate of the three branches is controlled by valves installed on each branch, and the flow rate and temperature are monitored by flow meters and thermocouples installed on each branch. The basis for flue gas recirculation is that plastic polymer materials are mainly composed of carbon and hydrogen elements. The gaseous products generated by their combustion, as well as the pyrolysis gas generated by cracking, contain a large amount of water vapor and carbon dioxide after combustion in the combustion furnace. Both of these substances have been proven to be excellent gasifying agents, and the gasification effect is positively correlated with temperature. The flue gas generated by combustion happens to have a high temperature, which can effectively improve its gasification effect. Therefore, recirculating part of the flue gas back to the gasifier can reduce the external water vapor supply, achieve water and energy saving, and effectively promote the gasification reaction of materials. It has a significant effect on reducing tar products. In addition, water vapor can also react with the pyrolysis residue to form water gas reaction, further reducing the heat loss on ignition of the incinerator ash. The first branch 3-1 is equipped with a separate first heating jacket 3-4 because it leads to the pyrolysis gas layer 1-2, which may contain large-molecule tar products. High-temperature steam can effectively promote their further pyrolysis into smaller-molecule gases. Therefore, a separate first heating jacket 3-4 is provided for the first branch 3-1. The second branch 3-2 and the third branch 3-3 are not equipped with heating jackets because both branches lead to the material layer. Excessive temperature in the material layer would exacerbate the volatilization of radioactive nuclides on the material, negatively impacting flue gas purification. Excessively high circulating flue gas temperatures would inevitably raise the material layer temperature; therefore, heating jackets are not provided for the second branch 3-2 and the third branch 3-3.

[0030] Preferably, the steam mixing system consists of a low-temperature steam inlet 4-1, a heating jacket 4-2, a first valve 4-3, and a mixing pipe 4-4. First, liquid water is heated into low-temperature steam by a steam generator, and then enters the heating jacket 4-2 through the low-temperature steam inlet 4-1. The heating jacket 4-2 is located in the main flue gas outlet pipe 5-3. The steam is indirectly heated by the waste heat of the flue gas in the heating jacket 4-2. The heated steam then enters the main flue gas circulation pipe 3-7 through the mixing pipe 4-4. The steam mixing flow rate is controlled by the opening degree of the first valve 4-3.

[0031] Preferably, the combustion system consists of a second ignition system 5-1, a combustion chamber 5-2, a flue gas duct 5-3, a fourth thermocouple 5-4, a fifth thermocouple 5-5, a third pressure gauge 5-6, and a fourth pressure gauge 5-7. The pyrolysis gas, mixed with air, enters the combustion chamber 5-2 and is ignited by the second ignition system 5-1. After stable combustion is achieved, the second ignition system 5-1 ceases operation. The flue gas generated by combustion flows out from the flue gas duct 5-3 and is discharged after passing through the downstream flue gas after-treatment stage. During this process, the temperatures above and below the combustion furnace are monitored by the fourth thermocouple 5-4 and the fifth thermocouple 5-5, respectively; the pressure at the top of the gasifier is monitored by the third pressure gauge 5-6; and the pressure at the bottom of the furnace is monitored by the fourth pressure gauge 5-7.

[0032] Preferably, the ash storage and ashing device consists of an ash storage and ashing chamber 6-1, a microwave generating component 6-2, and a baffle plate 6-3. After the bottom ash in the gasifier falls into the ash storage and ashing chamber, the residual carbon in the bottom ash is heated by microwaves emitted by the microwave generating component to continue the gasification reaction. When the bottom ash accumulates to a certain amount, the baffle plate is opened to discharge the bottom ash.

[0033] Example 2 The specific process steps of the radioactive combustible solid waste treatment method involved in this embodiment are as follows: Step 1, Material Pre-processing: Pre-process the materials to be processed, such as sorting and packaging, and finally package the materials to be processed into material packages of relatively uniform size.

[0034] Step 2: Preheating of Combustion Furnace 5: Open the second valve 2-4 for secondary air inlet, start the second heating jacket 2-5 to preheat the secondary air, and start the main induced draft fan at the tail end of the device. A negative pressure is created within the system, and air enters the combustion furnace 5 through the secondary air duct 2-2. Adjust the power of the second heating jacket 2-5 so that the preheated secondary air temperature reaches approximately 200 degrees Celsius. This temperature is detected by the third thermocouple 2-6. Start the second ignition system 5-1, which injects diesel fuel into the combustion furnace 5. The diesel fuel spray mixes with the air and is ignited by the spark plug of the second ignition system 5-1. By adjusting the valve opening 2-4, control the air volume and the injected diesel fuel volume to be near the stoichiometric air-fuel ratio and maintain stable combustion. This process continues until the temperature in the combustion furnace rises to approximately 600–1200 degrees Celsius.

[0035] Step 3, Gasifier 1 Start-up: Turn on the primary air blower, open the primary air supply pipe valve 1-11, open the first baffle of the feeding mechanism 1-1, the material bag falls onto the second baffle of the feeding mechanism 1-1, close the first baffle, open the second baffle, the material bag falls onto the upper grate 1-4 of the gasifier, close the second baffle. Start the first ignition system 1-6, inject diesel spray into the gasifier 1, the spark plug ignites the spray, the generated high-temperature flame ignites the lower layer of material, close the first ignition system 1-6. Control the primary air flow by adjusting the opening of the primary air valve until the material layer temperature can stably reach about 500 degrees Celsius, this temperature is based on the temperature detected by the second thermocouple 1-9. After the lower layer of material is stably burning, the heat released by combustion heats the upper layer of material, the upper layer of material undergoes oxygen-deficient pyrolysis, the generated pyrolysis gas flow is directed to the pyrolysis gas pipe 2-1, and mixed with the preheated secondary air before entering the combustion furnace 5 for combustion. The secondary air supply is adjusted by regulating the opening of the second valve 2-4 in the secondary air duct to regulate the combustion state of the pyrolysis gas in the combustion furnace 5 until the temperature at the top of the combustion furnace stabilizes within the range of 800–1200 degrees Celsius. This temperature is detected by the fourth thermocouple 5-4. During the material gasification process, some solid residue, namely bottom ash, is generated along with the gaseous products. The bottom ash contains unreacted solid carbon residue. Under gravity, the bottom ash falls into the ash storage and ashing chamber connected to the bottom of the gasifier. Simultaneously, the microwave generator emits microwaves into the ash storage and ashing chamber to heat the carbon residue in the bottom ash, causing it to continue reacting into gaseous products and further reducing the loss on ignition of the bottom ash.

[0036] Step 4: Start the flue gas recirculation system 3: Open the flue gas recirculation valve 3-8, turn on the induced draft fan 3-6, and open the valves of the first branch 3-1, the second branch 3-2, and the third branch 3-3. Adjust the opening degree of the flue gas recirculation valve 3-8 and the valve opening degree of each branch to adjust the flue gas flow rate of each branch to the preset parameter value (related to the exhaust gas emission level and the gasifier feed rate). At the same time, turn on the main pipeline heating jacket 3-5 and the first branch heating jacket 3-4, and adjust the heating jacket power so that the temperature in the first branch 3-1 is around 700 degrees Celsius, and the temperature in the second branch 3-2 and the third branch 3-3 is in the range of 200 to 750 degrees Celsius.

[0037] Step 5: Start the steam mixing system 4: This step is performed simultaneously with step (3). First, start the steam generator connected to the low-temperature steam inlet, and generate low-temperature steam of about 100-150 degrees Celsius. The low-temperature steam enters the flue gas waste heat heating jacket 4-2 through the steam inlet 4-1, and is heated by the waste heat of the flue gas. By controlling the pumping rate and power of the steam generator, the steam flow rate is adjusted and adjusted to the preset value (related to the exhaust gas emission level and the amount of feed into the gasifier). The steam after secondary heating by the waste heat enters the flue gas circulation pipe 3-7 through the mixing pipe 4-4, and mixes with the circulating flue gas, flowing together through each branch into the gasifier 1.

[0038] Step 6, Ash Discharge: After the device system has been running for a period of time, open the bottom plate of the ash storage and ashing device to discharge the bottom ash stored in the ash storage box and ashing chamber.

[0039] In this embodiment, through flue gas recirculation and external steam supplementation, the materials in the gasifier undergo a steam-introduced pyrolysis reaction. Specifically, the residual carbon, such as pyrolyzed coke from the char layer, reacts with steam to form water-gas, further reducing the ash loss on ignition. Under the action of steam, the molecular chains of the pyrolysis layer materials break down more rapidly, accelerating the pyrolysis efficiency. Large molecular intermediates in the pyrolysis gas, such as tar-like substances, react with steam to further decompose into smaller molecular gases, effectively suppressing tar production. In summary, introducing steam into the oxygen-deficient self-sustaining pyrolysis process effectively suppresses tar production through the chemical action of steam, improving the adaptability of the pyrolysis process to plastic polymer waste. Simultaneously, by utilizing the steam products and CO2 products in the flue gas, some additional water and energy consumption is saved, and the waste heat of the flue gas is used to heat the externally supplemented low-temperature steam, saving some additional energy consumption for obtaining high-temperature steam. Meanwhile, an ash storage and ashing device integrating ash storage and microwave ashing functions is installed at the bottom of the gasifier. While collecting and temporarily storing the bottom ash, microwaves are used to heat the residual carbon in the bottom ash, causing it to completely gasify, thus further reducing the loss on ignition rate of the bottom ash. The above technologies make the process proposed in this invention both economical and effective.

[0040] Example 3 The difference between this embodiment and embodiment 2 is that a material stirring mechanism is installed in the pyrolysis section 1-3. The stirring mechanism can agitate the material, solve problems such as uneven material accumulation and uneven heating, and improve the material combustion and pyrolysis process.

[0041] Example 4 The difference between this embodiment and embodiment 2 is that the second branch 3-2 of flue gas recirculation is cancelled, and only the first branch 3-1 and the third branch 3-3 are set. That is, the flue gas mixed with external steam enters the gasifier 1 from the bottom of the upper grate 1-4 and the cracked gas reforming section 1-2, respectively, which simplifies the pipeline layout.

[0042] Example 5 The difference between this embodiment and embodiment 2 is that the flue gas recirculation valves 3-8 are closed, the flue gas recirculation process is canceled, and steam is supplied only through steam mixing into system 4, which simplifies the process matching difficulty and operation difficulty.

[0043] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A radioactive combustible solid waste treatment apparatus, characterized by, It includes: Gasification furnace (1), mixed wind system (2), flue gas recirculation system (3), steam mixing system (4), combustion furnace (5) and ash storage ash device (6); wherein, the gasification furnace (1) includes feeding mechanism (1-1), cracking gas reforming section (1-2), material cracking section (1-3), first ignition system (1-6), first thermocouple (1-7), second thermocouple (1-8), first pressure gauge (1-9), second pressure gauge (1-10) and primary air supply pipeline (1-11); the flue gas recirculation system (3) includes flue gas circulation first branch (3-1), second branch (3-2), third branch (3-3), first heating jacket (3-4), flue gas circulation main pipeline heating jacket (3-5), induced draft fan (3-6), flue gas recirculation valve (3-8), flue gas circulation main pipeline (3-7), and each branch valve, thermocouple, flowmeter; part of the flue gas generated by combustion is introduced back to the gasification furnace (1) from the flue gas outlet main pipeline (5-3) by the induced draft fan (3-6), the total flow of recirculated flue gas is controlled by the opening of the flue gas recirculation valve (3-8) installed on the circulation main pipeline (3-8), the recirculated flue gas is heated by the flue gas circulation main pipeline heating jacket (3-5), and enters the gasification furnace (1) through the first branch (3-1), the second branch (3-2) and the third branch (3-3) respectively; wherein, the first branch (3-1) is provided with a first heating jacket (3-4) for reheating the flue gas flowing through the first branch (3-1); the steam mixing system (4) includes low-temperature steam inlet (4-1), heating jacket (4-2), first valve (4-3) and mixing pipeline (4-4); liquid water is heated into low-temperature steam by a steam generator, enters the heating jacket (4-2) from the low-temperature steam inlet (4-1), and the heating jacket (4-2) is located in the flue gas outlet main pipeline (5-3); the water vapor is indirectly heated by the flue gas waste heat in the heating jacket (4-2), and the heated water vapor enters the flue gas circulation main pipeline (3-7) through the mixing pipeline (4-4); the water vapor mixing flow is controlled by the opening of the first valve (4-3).

2. A radioactive combustible solid waste treatment apparatus according to claim 1, wherein The gasification furnace (1) further comprises an upper grate (1-4) and a lower grate (1-5) arranged vertically, the material is fed into the gasification furnace (1) through the feeding mechanism (1-1), and is accumulated on the upper grate (1-4); a material layer to be combusted is formed in the material cracking section (1-3), air is introduced from the primary air supply pipeline (1-11), and the first ignition system (1-6) can ignite the material layer.

3. A radioactive combustible solid waste treatment apparatus according to claim 2, wherein, The material layer to be combusted formed in the material cracking section (1-3) is divided into an ash layer, a coking layer and a cracking layer from bottom to top, steam is introduced into the gasification furnace (1) from three positions below the upper grate (1-4), the middle of the material cracking section (1-3) and the bottom of the cracking gas reforming section (1-2) respectively.

4. A radioactive combustible solid waste treatment apparatus according to claim 1, wherein The air mixing system (2) comprises a cracking gas pipeline (2-1), a secondary air pipeline (2-2), a secondary air flow meter (2-3), a second valve (2-4), a second heating jacket (2-5) and a third thermocouple (2-6); cracking gas flows out of the gasifier (1), passes through the cracking gas pipeline (2-1), the cracking gas pipeline (2-1) communicates with the secondary air pipeline (2-2), the secondary air flow is controlled by the opening degree of the second valve (2-4), monitored by the secondary air flow meter (2-3), and the temperature is monitored by the third thermocouple (2-6); the secondary air is preheated by the second heating jacket (2-5) before mixing with the cracking gas, and then mixed with the cracking gas to enter the combustion furnace (5).

5. A radioactive combustible solid waste treatment apparatus according to claim 1, wherein The combustion furnace (5) comprises a second ignition system (5-1), a combustion chamber (5-2), a flue gas pipeline (5-3), a fourth thermocouple (5-4), a fifth thermocouple (5-5), a third pressure gauge (5-6) and a fourth pressure gauge (5-7); the cracking gas mixed with air enters the combustion chamber (5-2) and is ignited by the second ignition system (5-1); the flue gas generated by combustion can flow out of the flue gas pipeline (5-3) and be discharged after the rear-end flue gas post-processing link.

6. A radioactive combustible solid waste treatment apparatus according to claim 1, wherein The ash storage and ashing device (6) comprises an ash storage and ashing chamber (6-1), a microwave generating component (6-2) and a plugboard (6-3); the solid residues (bottom ash) remaining after gasification of the material in the gasifier (1) are first discharged into the ash storage and ashing chamber (6-1) for temporary storage, at the same time, the microwave generating component (6-2) emits microwaves to heat the residual carbon in the bottom ash, so that it can be completely reacted.

7. A method of treating radioactive combustible solid waste based on the apparatus for treating radioactive combustible solid waste according to any one of claims 1 to 6, characterized by, The method comprises the following steps: Preprocessing the material: preprocessing the material to be processed, and packaging the material to be processed into a material package to be processed; Preheating the combustion furnace (5): opening the second valve (2-4), starting the second heating jacket (2-5) to preheat the secondary air, starting the main induced draft fan at the tail end of the device, forming a negative pressure in the system, and air entering the combustion furnace (5) from the secondary air pipeline (2-2); starting the second ignition system (5-1), injecting diesel oil from the second ignition system (5-1) into the combustion furnace (5), the diesel oil spray mixes with air, and is ignited by the spark plug of the ignition system (5-1); Starting the gasifier (1): open the primary air blower, open the valve of the primary air supply pipeline (1-11), open the first plug of the feeding mechanism (1-1), the material bag falls on the second plug of the feeding mechanism (1-1), close the first plug, open the second plug, the material bag falls on the upper grate (1-4) of the gasifier (1), close the second plug; start the first ignition system (1-6), spray diesel spray into the gasifier (1), the ignition plug ignites the spray, the high temperature flame produced ignites the lower layer of material, closes the first ignition system (1-6); control the primary air flow by adjusting the valve opening of the primary air supply pipeline (1-11) until the material layer temperature can stably reach the preset combustion temperature, after the lower layer of material is stably combusted, the heat released by combustion heats the upper layer of material, the upper layer of material undergoes oxygen-deficient cracking, the cracking gas flows to the cracking gas pipeline (2-1), and after being mixed with the preheated secondary air, enters the combustion furnace (5) for combustion; Open the flue gas recirculation system (3): open the flue gas recirculation valve (3-8), open the induced draft fan (3-6), open the valves of the first branch (3-1), the second branch (3-2) and the third branch (3-3); open the first heating jacket (3-4) and the flue gas circulation main pipeline heating jacket (3-5); Open the steam mixing system (4): first open the steam generator connected with the low-temperature steam inlet (4-1), and generate low-temperature steam of about 100-150 degrees Celsius from the steam generator, the low-temperature steam enters the heating jacket (4-2) through the low-temperature steam inlet (4-1) and is heated and warmed by the waste heat of flue gas; the steam after secondary heating by waste heat enters the flue gas circulation main pipeline (3-7) through the mixing pipeline (4-4), mixes with circulating flue gas, and flows through each branch into the gasifier (1); Ash discharge: the bottom ash falls into the ash storage and incineration chamber (6-1) connected to the bottom of the gasifier (1) under the action of gravity, at the same time, the microwave generating part (6-2) emits microwaves to the ash storage and incineration chamber (6-1) to heat the residual carbon in the bottom ash to continue the reaction to gaseous products; after a period of system operation, open the bottom plug (6-3) of the ash storage and incineration device to discharge the bottom ash stored in the ash storage and incineration chamber (6-1).

8. The process for the treatment of radioactive combustible solid waste according to claim 7, characterized in that, Preheat the combustion furnace (5), specifically: control the temperature in the combustion furnace (5) to 600-1200 degrees Celsius.

9. The process for the treatment of radioactive combustible solid waste according to claim 7, characterized in that, Open the flue gas recirculation system (3), specifically: control the temperature in the first branch (3-1) to 600-700 degrees Celsius, and control the temperature in the second branch (3-2) and the third branch (3-3) to 200-750 degrees Celsius.

10. The process for the treatment of radioactive combustible solid waste according to claim 7, characterized in that, The produced cracking gas stream is fed to the cracking gas pipeline (2-1), and mixed with the preheated secondary air to enter the combustion furnace (5) for combustion. By adjusting the opening of the second valve (2-4), the amount of secondary air supply is adjusted to regulate the cracking gas combustion state in the combustion furnace (5), until the temperature at the upper part of the combustion furnace (5) is stabilized at 800-1200 degrees Celsius, which is detected by the fourth thermocouple (5-4).

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