Integrated grate-type waste gasification combustion method

Abstract

The present application relates to garbage flue gas treatment technical field, specifically for integrated grate type garbage gasification combustion method, comprising the following steps: S1: drying; S2: pyrolysis gasification; S3: burnout; S4: synthesis gas combustion; S5: waste heat recycling; S6: high temperature flue gas circulation; S7: combustion air supply; S8: tail gas treatment; S9: low temperature flue gas circulation.The present application is based on integrated grate garbage continuous gasification combustion treatment, and the comprehensive separation effect of garbage layer is better, and staggered primary air is more easily penetrated into the layer, and the heat carried by high temperature flue gas and low temperature flue gas is fully utilized, combined with three furnace body structure, heat utilization rate and reaction rate are improved, synthesis gas quality is improved, secondary pollution control is better, and at the same time, steel structure working temperature is also controlled, and system reliability is improved.

Description

Technical Field

[0001] This invention relates to the field of waste flue gas purification technology, specifically to an integrated grate-type waste gasification and combustion method. Background Technology

[0002] With rapid economic development and accelerating urbanization, the amount of solid waste generated is increasing rapidly. Household waste has become a major factor restricting social development, not only occupying vast amounts of land but also causing significant harm to the ecological environment and human health. Currently, waste treatment technologies mainly include incineration, sanitary landfill, composting, and waste recycling. Incineration, as one of the main methods of household waste disposal, has significant effects in reducing volume and quantity, and can achieve energy utilization, which aligns with my country's sustainable development strategy and has great application value.

[0003] Incineration generates pollutants such as SOx, NOx, particulate matter, heavy metals, and dioxins during the waste treatment process, causing serious secondary pollution to the environment. Therefore, controlling secondary pollution from waste incineration is of paramount importance. For many years, continuous research has been conducted on the control of secondary pollution from waste incineration. Among these, waste pyrolysis gasification incineration technology, due to its lower production of secondary pollutants, has gradually been pushed towards industrial application.

[0004] Waste pyrolysis gasification incineration technology refers to the process of burning waste under anaerobic or oxygen-deficient conditions, causing the large molecules of organic components in the waste to break down and produce small-molecule gases, tar, and residue. Because it burns under anaerobic or oxygen-deficient conditions, it produces relatively few harmful gases such as dioxins and SOx during the combustion process, thus causing less secondary pollution.

[0005] The existing waste pyrolysis gasification system and method have the following disadvantages in operation: (1) The system has high requirements for the calorific value and moisture content of the raw waste. The waste needs to be sorted, dried and other pre-treatment processes, which increases the pre-treatment cost; (2) Waste often accumulates and forms sheds in the pyrolysis gasification chamber. The material is unevenly distributed, the pyrolysis gasification is insufficient, and coking is easy to occur on the grate. After the device has been running for a period of time, the coke sticks to the grate, which affects the pyrolysis gasification efficiency, makes it impossible to unload the coke, and the device cannot operate continuously; (3) The waste residue generated is not treated in an integrated manner. An additional waste residue treatment system is set up, which causes a waste of resources and energy; (4) The heat circulation system in the system is simply designed. The energy of each heat treatment stage of the system is not fully utilized, which causes energy waste and low energy utilization rate.

[0006] To address the aforementioned issues, Chinese scholars have conducted extensive research and made numerous improvements to waste incinerators and secondary pollutant control technologies. With technological advancements and increasingly stringent environmental protection requirements, technologies such as: mechanical grate waste gasification incinerators and their treatment methods (CN105402735B), double-layer mechanical grate waste gasification incinerators and their treatment methods (CN105423306B), mechanical grate single-furnace waste gasification incineration systems and their treatment methods (CN105444183B), and mechanical grate waste gasification incineration systems and their treatment methods (CN10562732) have emerged. Emerging gasification incineration technologies and methods, such as 2B) and double-layer mechanical grate waste gasification incineration systems and their treatment methods (CN105402736B), have improved the control level of secondary pollutants, refined the process control process, and obtained extensive experimental verification. However, the following problems exist: 1. In the waste drying stage, a uniform temperature of drying air is used for drying. If the drying air temperature is too low, the waste may not dry completely, affecting the subsequent gasification and combustion efficiency. If the drying air temperature is too high, the required energy and treatment costs increase, and the waste may coke on the grate, affecting the normal operation of the grate. 2. There are no independent drying and gasification stages set according to the different temperatures required for waste drying and gasification, resulting in uneven heat distribution and low heat utilization. At the same time, waste drying and gasification occur simultaneously, and the heat conversion processes in each stage are interdependent, making process control more difficult, secondary pollutants harder to control, and drying and gasification efficiency limited. 3. There is only one flue gas recirculation pipeline or no flue gas recirculation pipeline, and the hot flue gas from other treatment units cannot participate in the system treatment, resulting in low energy utilization efficiency. Meanwhile, no corresponding flue gas was set up for mixing and recombination of the syngas produced by pyrolysis gasification, resulting in a low CO / H2 ratio and low purity of the syngas. Summary of the Invention

[0007] This invention provides an integrated grate-type waste gasification combustion method to solve the technical problem that the energy of waste combustion is not fully utilized in the prior art.

[0008] This invention provides the following technical solution: an integrated grate-type waste gasification and combustion method, comprising the following steps:

[0009] S1: Drying, gradient temperature drying, after the waste is dried, dry flue gas and dry waste are produced;

[0010] S2: Pyrolysis gasification, which pyrolyzes and gasifies the dried waste to produce bottom ash and pyrolysis gasification synthesis flue gas. The dried flue gas is fed into the gasifier to mix and reform the synthesis flue gas.

[0011] S3: Combustion, the bottom ash is combusted at high temperature, producing ash and flue gas; the ash is utilized for resource recovery, and the flue gas is returned to be mixed and reformed with pyrolysis gasification synthesis flue gas and dried flue gas.

[0012] S4: Syngas combustion, which involves secondary high-temperature combustion of the reformed pyrolysis gasification synthesis flue gas to produce high-temperature flue gas, while simultaneously performing high-temperature denitrification;

[0013] S5: Waste heat recovery and utilization, high-temperature flue gas passes through the boiler system and heat exchanger to generate low-temperature flue gas, water steam, and heat the air;

[0014] S6: High-temperature flue gas circulation, extracting high-temperature flue gas from the boiler system and supplying it into S1, S2 and S4 respectively;

[0015] S7: Combustion air supply, which draws air from the garbage storage pit, heats it through the boiler system to form heated air, and then supplies it into S3 and S4;

[0016] S8: Exhaust gas treatment. Low-temperature flue gas is introduced into the exhaust gas treatment system and undergoes desulfurization, activated carbon adsorption and dust removal in sequence before being introduced into the chimney for emission in compliance with standards.

[0017] S9: Low-temperature flue gas circulation, low-temperature flue gas is extracted from the end of the flue gas purification system and supplied to S1 and S2 respectively; the low-temperature flue gas is supplied to S1 in the following ways: direct supply and mixed supply. The mixed supply is to mix the low-temperature flue gas with the high-temperature flue gas to form a circulating mixed flue gas before supplying it. The temperature of the circulating mixed flue gas is distributed in a gradient.

[0018] Furthermore, in S6, the high-temperature flue gas temperature is 500-550℃; in S7, the heating air temperature is 100-150℃; in S9, the low-temperature flue gas temperature is 120-150℃, and the circulating mixed flue gas temperature is 180-250℃, 250-300℃, and 300-350℃, respectively.

[0019] Beneficial effects: High-temperature flue gas supplied to S1, S2, and S4 can fully utilize its heat for drying, pyrolysis, gasification, and combustion of waste. Heated air supplied to S3 and S4 can provide the oxygen required for combustion. Low-temperature flue gas has a suitable temperature and is pollution-free, making it suitable for continued supply and utilization. Circulating mixed flue gas supplied to S1 can provide the flue gas required for gradient drying.

[0020] Furthermore, in S6, the oxygen content of the high-temperature flue gas is 6%-10%; the oxygen content of the heated flue gas is 21%; and the oxygen content of the low-temperature flue gas is 8%-12%.

[0021] Beneficial effects: In this application, most of the gas comes from internal circulation. At the same time, the pyrolysis gasification combustion of waste needs to be carried out in an anaerobic or hypoxic state. Therefore, the oxygen content of the limiting gas is low, which reduces the amount of harmful substances such as SOx and dioxins synthesized during the gasification combustion process, thus reducing secondary pollution.

[0022] Furthermore, the drying temperature in S1 is 150-500℃, and the drying flue gas temperature is 450-500℃.

[0023] Beneficial effects: S1 employs a gradient temperature drying method for waste, which allows for the full evaporation of residual moisture in the waste, producing dry flue gas with a high moisture content for subsequent use. This results in high drying efficiency and prevents coking caused by excessively high local temperatures. Furthermore, the small portion of waste undergoes pyrolysis at the rear, which helps improve pyrolysis gasification efficiency.

[0024] Furthermore, the pyrolysis gasification temperature in S2 is 500-850℃, and the combustion temperature in S3 is 850-950℃.

[0025] Beneficial effects: At this temperature in S2, pyrolysis and gasification can proceed fully, effectively pyrolyzing and gasifying the waste. Continued high-temperature combustion of the bottom ash can decompose or seal residual dioxins and other substances within the solid waste. Simultaneously, the flue gas produced during continued combustion can be returned to the pyrolysis and gasification process, improving overall energy utilization efficiency.

[0026] Furthermore, in the S4 process, the pyrolysis gasification synthesis flue gas from the reforming process contains 10-15% nitric oxide, 5-8% hydrogen, 5-8% methane, and a secondary high-temperature combustion temperature of 900-1050℃.

[0027] Beneficial effects: The CO / H2 ratio in the reformed pyrolysis gasification synthesis flue gas is improved, facilitating the purification and reuse of the synthesis gas. The high secondary combustion temperature ensures thorough combustion of the pyrolysis gasification synthesis flue gas, reducing the formation of harmful substances. Simultaneously, high-temperature denitrification is highly efficient at this temperature, removing most of the nitrogen (N) element.

[0028] Furthermore, S6 also includes high-temperature dust removal at 600-650℃, and the high-temperature flue gas after dust removal is supplied to S1, S2 and S4 respectively.

[0029] Beneficial effects: Introducing high-temperature dust removal treatment can preliminarily treat the fly ash generated in the syngas combustion flue gas, reduce secondary pollution caused by fly ash, and avoid the impact of fly ash on the flue gas circulation pipeline; the high temperature of the flue gas after high-temperature dust removal can provide sufficient hot flue gas for S1, S2 and S4, thereby improving the overall energy utilization efficiency.

[0030] Furthermore, in S8, the low-temperature flue gas temperature is 220-250℃, the desulfurization temperature is 220-250℃, the dust removal temperature is 180-220℃, and the chimney emission temperature is 150-180℃.

[0031] Beneficial effect: Desulfurization at 220-250℃ can improve the desulfurization effect.

[0032] This invention also provides an integrated grate waste gasification combustion system, comprising a gasification combustion furnace for waste drying and gasification; a boiler system for combustion and heat exchange of the gasified gas and syngas; a flue gas purification system for treating the gas; an air supply system for providing an external air source to the system; and a flue gas circulation system for internal circulation of the system's flue gas. The gasification combustion system, boiler system, and tail gas treatment system are all equipped with flue gas inlets and outlets. The flue gas outlet of the gasification combustion furnace is connected to the flue gas inlet of the boiler system, and the flue gas outlet of the boiler system is connected to the flue gas inlet of the tail gas treatment system. An integrated grate is provided in the gasification combustion furnace.

[0033] Beneficial effects of this invention:

[0034] 1. Compared to existing technologies that use overall drying during the drying stage, this invention mixes the high-temperature flue gas generated after syngas combustion and the exhaust gas generated after tail gas treatment in different proportions to generate mixed circulating gases with different temperature gradients for drying. This improves the drying effect of waste and avoids the formation of localized high temperatures and coking in the initial drying stage. Simultaneously, a small amount of waste undergoes pyrolysis and gasification in the later stages of drying, which is beneficial to the efficiency of pyrolysis and gasification. Specifically, the first stage drying temperature is 180-250℃. Since the waste is located at the inlet and is relatively large and moves slowly, using a higher temperature in this stage could cause coking of the waste at the lower levels on the grate. The second stage temperature is 250-300℃, which is a rapid drying stage, so the temperature needs to be increased to dry most of the moisture in the waste. The third stage temperature is 300-350℃, where the temperature is further increased to further dry the moisture in the waste. At the same time, combined with the temperature inside the furnace, a small portion of the waste undergoes preliminary pyrolysis and gasification at this temperature, improving the waste processing efficiency.

[0035] 2. Compared to existing technologies that do not fully utilize the dried flue gas, this invention introduces the dried flue gas into the gasification chamber. Firstly, it utilizes the significant heat contained in the dried flue gas to heat the gasification chamber, improving energy utilization efficiency. Secondly, it utilizes the large amount of water vapor contained in the dried flue gas; introducing it into the gasification chamber allows for the recombination of the air composition within the chamber, increasing the CO / H2 ratio in the syngas and facilitating its purification and reuse. Thirdly, it avoids the condensation of water vapor on the furnace wall during its ascent, preventing localized low temperatures within the drying chamber and thus reducing the overall temperature.

[0036] 3. Compared to existing technologies that do not perform burnout treatment on ash slag, this invention designs a burnout chamber to treat the ash slag produced by pyrolysis and gasification, allowing the ash slag to continue burning at high temperatures. This not only facilitates the high-temperature decomposition of harmful substances such as dioxins remaining in the ash slag, but also allows the high-temperature gases generated by combustion to be returned to the gasification chamber, maintaining the temperature within the gasification chamber and improving energy utilization efficiency. Simultaneously, the returned high-temperature flue gas agitates the syngas within the gasification chamber, promoting the recombination reaction of the syngas.

[0037] 4. Compared with existing technologies that only have partial or no flue gas recirculation pipelines, this invention adds high-temperature flue gas recirculation and low-temperature flue gas recirculation in the waste pyrolysis gasification combustion process. The flue gas generated in each stage is recycled back for drying, pyrolysis gasification and syngas combustion, which improves the energy utilization efficiency of the whole system and the steam supply parameters at the steam consumption end, and also better controls secondary pollutants.

[0038] 5. Compared with the prior art, which does not reorganize the syngas produced by pyrolysis gasification and directly combusts it, the syngas in this application has a higher CO / H2 ratio after reorganization. The syngas does not need to undergo gas phase combustion and can directly enter the subsequent flue gas syngas purification process for purification and reuse.

[0039] 6. Side Beam Protection and Air Supply: Low-temperature flue gas is supplied to the primary air ducts of the gasification chamber side beams and the drying chamber side beams to absorb excess heat from the primary air chamber and waste material layer reaction, control the working temperature of the side beam steel structure, protect the side beam steel structure, solve the problem of high temperature affecting the strength and rigidity of the steel structure in the existing technology, and improve the service life of the furnace body. At the same time, it can also supply air to the drying chamber and gasification chamber through integrated grate bars, reheat and reuse, and control the oxygen supply for drying and gasification. Attached Figure Description

[0040] Figure 1 This is a flowchart illustrating an embodiment of the integrated grate-type waste gasification and combustion method of the present invention;

[0041] Figure 2 This is a schematic diagram of the integrated grate waste gasification and combustion system according to an embodiment of the present invention;

[0042] Figure 3 This is a schematic diagram of the structure of the gasification combustion furnace according to an embodiment of the present invention;

[0043] Figure 4 This is a schematic diagram of the boiler system and air supply system according to an embodiment of the present invention;

[0044] Figure 5 This is a schematic diagram of the flue gas treatment system according to an embodiment of the present invention;

[0045] Figure 6 This is a schematic diagram of the flue gas recirculation system according to an embodiment of the present invention. Detailed Implementation

[0046] The following detailed description illustrates the specific implementation method:

[0047] The markings in the accompanying drawings include:

[0048] Gasification combustion furnace 1, furnace frame 101, feeding bin 102, furnace body 103, slag discharge port 104, pusher 105, integrated grate body 106, drying chamber 107, gasification chamber 108, combustion chamber 109, flue gas passage 110, primary air hole 111, secondary air hole 112, tertiary air hole 113, reheat air hole 114, ignition and combustion aid hole 115;

[0049] Boiler system 2, boiler body 201, SNCR injection device 202, combustion chamber 203, heat exchanger 204, exhaust gas outlet 205, steam consumption end 206, fly ash conveying outlet 207, high temperature dust collector 208, first fly ash treatment 209;

[0050] Air supply system 3, blower 301, first air supply pipeline 302, second air supply pipeline 303;

[0051] 4. Flue gas recirculation system, first flue gas duct 401, second flue gas duct 402, first manifold 403, second manifold 404, third manifold 405, fourth manifold 406, fifth manifold 407, branch pipe 408, high temperature exhaust fan 409, low temperature exhaust fan 410.

[0052] 5. Flue gas purification system, 501. Gas scrubbing tower, 502. Bag filter, 503. Exhaust fan, 504. Chimney, 505. Fly ash conveyor belt, 506. Deacidification injection device, 507. Second fly ash treatment.

[0053] Example

[0054] For details, please refer to the attached document. Figure 1-6An integrated grate waste gasification combustion system includes a gasification combustion furnace 1, a boiler system 2, an air supply system 3, and a flue gas circulation system 4. The gasification combustion furnace 1 includes a furnace frame 101, and a feeding bin 102, a furnace body 103, and a slag discharge port 104 arranged sequentially along the feeding direction on the furnace frame 101. A material stacking sealing section is provided between the feeding bin 102 and the furnace body 103. A pusher 105 is provided on the furnace frame 101, located below the feeding bin 102, for pushing the waste in the feeding bin 102 into the furnace chamber of the furnace body 103. The furnace body 103 includes a furnace shell and an integrated grate body 106 disposed within the furnace shell. The integrated grate body 106 includes two side beam assemblies. The integrated fixed grate and integrated movable grate are arranged between two side beam assemblies. The integrated fixed grate includes several fixed grate plates fixedly connected to the side beam assemblies. The integrated movable grate includes several movable support plates arranged side by side. The movable support plates are located below the fixed grate plates. A movable grate plate connects two adjacent movable support plates. The fixed grate plates and movable grate plates are arranged alternately along the conveying direction. The bottom of the movable support plates is connected to the drive assembly. The side beam assembly is provided with a support and guide assembly for supporting and guiding the movement of the integrated movable grate. A primary air channel is provided inside the side beam assembly. Primary air cavities are opened inside the fixed grate plates and movable grate plates along the length direction. The primary air cavities are connected to the primary air channel.

[0055] In this embodiment, two sets of integrated grate bodies 106 are arranged along the conveying direction of waste in the furnace body 103. The first set of integrated grate bodies 106 and the furnace shell form a drying chamber 107, and the second set of integrated grate bodies and the shell form a gasification chamber 108. The tail end of the second set of integrated grate bodies 106 and the shell form a combustion chamber 109. The drying chamber 107, the gasification chamber 108, and the combustion chamber 109 are interconnected. Several primary air chambers are arranged below both sets of integrated grate bodies 106. Specifically, the furnace shell is an arched structure. The front and rear arches of the drying chamber 107 are provided with secondary air holes 112. The top of the drying chamber 107 is provided with a flue gas outlet. The furnace shell of 07 is also provided with an ignition and combustion aid hole 115 at the end. The drying chamber 107 can be heated and baked through the ignition and combustion aid hole 115 to improve the drying efficiency of the waste after entering the drying chamber 107. The gasification chamber 108 is also provided with secondary air holes 112 at the front and rear arches of the furnace shell, and the top of the furnace shell is provided with a flue gas passage 110. The flue gas passage 110 is provided with an ignition and combustion aid hole 115 on its wall. The flue gas passage 110 is connected to the boiler system 2. The top of the flue gas passage 110 is also provided with a tertiary air hole 113 and a reheat air hole 114. The bottom of the combustion chamber 109 is provided with a primary air hole 111, and the side wall is provided with an ignition and combustion aid hole 115. The flue gas outlet of the drying chamber 107 is connected to the secondary air vent 112 of the gasification chamber 108 through a pipe. The drying flue gas with a high moisture content is injected into the gasification chamber 108 by the drying flue gas exhaust fan. On the one hand, it plays a reforming role in the flue gas of the gasification chamber 108 and increases the proportion of CO and H2 in the flue gas. On the other hand, it can also prevent water vapor in the drying flue gas from condensing due to local low temperature in the drying chamber 107, thus reducing the heat value in the drying chamber 107.

[0056] Boiler system 2 includes a boiler body 201 and a heat exchanger 204 installed inside the boiler body 201. A flue gas passage 110 is connected to the boiler inlet. An SNCR injection device is also installed on the boiler inlet side wall. An exhaust gas outlet 205 is also installed at the lower end of the boiler body 201. The exhaust gas outlet 205 is connected to a flue gas purification system 5. The flue gas purification system 5 includes a scrubbing tower 501, a bag filter 502, an induced draft fan 503, and a chimney 504 connected in series along the exhaust direction. A fly ash conveyor belt is installed at the bottom of the scrubbing tower 502, and a deacidifying agent SNCR injection device 202 is installed on the top wall of the scrubbing tower 501. An activated carbon adsorption device is installed on the side wall of the scrubbing tower 501. A deacidifying agent (lime slurry can be used) is injected into the scrubbing tower 501 to remove acidic gases such as SOx, HCl, and HF from the flue gas and perform a low-temperature neutralization reaction. Activated carbon adsorbs heavy metals, dioxins, etc. in the flue gas. A bag filter collects fly ash from the flue gas and then uses a fly ash conveyor belt to transport the fly ash to the second fly ash treatment 507.

[0057] The air supply system 3 is mainly used to blow the gas in the waste storage pit into the combustion chamber 109 and the flue gas passage 110 through the blower 301 to assist combustion. Specifically, the blower 301 blows the gas in the storage pit into the heat exchanger 204 to make full use of the heat in the boiler for heat exchange. After heat exchange, it is divided into two air supply pipelines. The first air supply pipeline 302 is connected to the tertiary air hole 113 of the flue gas passage 110 to assist gas phase combustion. The second air supply pipeline 303 is connected to the primary air hole 111 of the combustion chamber 109 to assist solid phase waste residue combustion. The high-temperature flue gas generated by combustion in the combustion chamber 109 rises to the gasification chamber 108, which can increase the temperature in the gasification chamber 108. At the same time, it counteracts and disturbs the syngas generated by pyrolysis in the gasification chamber 108, which helps to reform the flue gas.

[0058] The flue gas recirculation system 4 includes a first flue gas pipeline and a second flue gas pipeline. The inlet end of the first flue gas pipeline is connected to the boiler body 201 for reusing the high-temperature flue gas in the boiler. The inlet end of the second flue gas pipeline is connected to the induced draft fan 503 in the flue gas purification system 5 for reusing the purified low-temperature flue gas. A high-temperature dust collector 208 is installed at the end of the first flue gas pipeline near the boiler body 201. A first fly ash treatment 209 is installed below the high-temperature dust collector 208 to remove fly ash from the flue gas and reduce the damage of fly ash to downstream equipment. The end of the first flue gas pipeline is connected to a high-temperature exhaust fan 409. The high-temperature exhaust fan 409 divides the first flue gas pipeline into two paths. One path is connected to the reheat air hole 114 in the flue gas pipeline through the first manifold 403. This high-temperature flue gas enters the top of the flue gas channel 110 to play a role in reheating and temperature regulation, which can reduce gas phase synthesis. The local temperature of the gas combustion is controlled to prevent excessive NOx production due to high temperatures, while ensuring the decomposition of dioxins. Another path is connected to several primary air chambers at the bottom of the drying chamber 107 and the gasification chamber 108 via the second manifold 404. The primary air entering the bottom of the drying chamber 107 is arranged in a gradient along the material conveying direction. In addition, the second manifold 404 in this embodiment is further divided into a branch pipe 408, which is connected to the secondary air hole 112 above the drying chamber 107 to increase the temperature of the drying flue gas.

[0059] A low-temperature exhaust fan 410 is installed at the end of the second flue gas pipeline. The second flue gas pipeline is further divided into a third manifold 405, a fourth manifold 406, and a fifth manifold 407. The third manifold 405 is connected to the second manifold 404 that enters the drying chamber 107. By mixing the low-temperature flue gas in the third manifold 405 with the high-temperature flue gas in the second manifold 404, the temperature of the primary air chamber in the drying chamber 107 is adjusted by regulating the valves in the pipeline, so that it is distributed in a gradient temperature increase. The fourth manifold 406 is connected to the side beam in the drying chamber 107, and the fifth manifold 407 is connected to the side beam in the gasification chamber 108. Since the flue gas in the second flue gas pipeline has been purified, the overall temperature of the flue gas is low (120-150℃). Introducing the flue gas into the side beam can reduce the working temperature of the side beam, protect the steel structure of the side beam, and at the same time provide air supply for the integrated grate.

[0060] Basic as Figure 1 As shown, the method for purifying flue gas from waste gasification combustion using a grate furnace includes the following steps:

[0061] S1: Drying, gradient temperature drying, after the waste is dried, dry flue gas and dry waste are produced;

[0062] Specifically, the waste to be processed is fed into the integrated grate body 106 of the drying chamber 107 for drying. As shown in the attached diagram, the integrated grate body 106 moves up and down to thoroughly break up the waste. The integrated grate body 106 of the drying chamber 107 is divided into three sections with stepped temperature drying along the waste conveying direction: 180-250℃, 250-300℃, and 300-350℃. The temperature inside the drying chamber 107 is 400-450℃. After drying, dried waste and dried flue gas are produced, with the flue gas temperature at 450-500℃.

[0063] S2: Pyrolysis gasification, which pyrolyzes and gasifies the dried waste to produce bottom ash and pyrolysis gasification synthesis flue gas. The dried flue gas is fed into the gasifier to mix and reform the synthesis flue gas.

[0064] Specifically, the dried waste is fed into the gasification chamber 108 onto the integrated grate body 106. Low-temperature flue gas at 120-150℃ is introduced below the side beams of the integrated grate body 106, while high-temperature flue gas at 500-550℃ is introduced into the moving section of the integrated grate. The temperature inside the combustion chamber is 500-850℃. After the dried waste completes pyrolysis and gasification, bottom ash is produced and discharged into the combustion chamber 109.

[0065] S3: Combustion, the bottom ash is combusted at high temperature, producing ash and flue gas; the ash is utilized for resource recovery, and the flue gas is returned to be mixed and reformed with pyrolysis gasification synthesis flue gas and dried flue gas.

[0066] Specifically, the bottom ash enters the combustion chamber 109 and continues to burn at 850-950℃. The resulting flue gas can be returned to the gasification chamber 108 to further heat the temperature, raising it to 700-800℃. The flue gas is then mixed and reformed with the pyrolysis gasification synthesis gas and the dried gas. The resulting syngas has a composition of 10-15% nitric oxide, 5-8% hydrogen, and 5-8% methane.

[0067] S4: Syngas combustion, which involves secondary high-temperature combustion of the reformed pyrolysis gasification synthesis flue gas to produce high-temperature flue gas, while simultaneously performing high-temperature denitrification.

[0068] Specifically, the reformed pyrolysis gasification flue gas is introduced into the combustion chamber 203 of boiler system 2 through flue gas passage 110. The inlet of combustion chamber 203 is equipped with combustion-supporting equipment to perform syngas combustion on the pyrolysis gasification flue gas at a combustion temperature of 900-1050℃. After syngas combustion, an SNCR injection device is used to denitrify the syngas combustion flue gas.

[0069] S5: Waste heat recovery and utilization; high-temperature flue gas passes through a boiler system and heat exchanger to generate low-temperature flue gas, steam, and heated air.

[0070] Specifically, the steam generated from the syngas combustion flue gas after heat exchange in heat exchanger 204 can be used at the steam consumption end 206, which includes, but is not limited to, steam power generation and steam heating.

[0071] S6: High-temperature flue gas circulation, extracting high-temperature flue gas from the boiler system and supplying it into S1, S2 and S4 respectively;

[0072] Specifically, the high-temperature flue gas after heat exchange is introduced into the high-temperature dust collector 208 for fly ash treatment, and the fly ash settled at the bottom is transported to the first fly ash treatment 209. Then, the high-temperature exhaust fan 409 extracts the high-temperature flue gas along the first flue gas duct 401, and a portion of the high-temperature flue gas returns to the combustion chamber 203 along the first manifold 403 for syngas combustion. A portion of the high-temperature flue gas is successively supplied along 404 to the integrated grate moving section of the gasification chamber 108 and the combustion chamber 109 for pyrolysis gasification and drying of the waste. Another portion of the high-temperature flue gas is supplied along the branch pipe 408 through the secondary air hole 112 to the upper part of the drying chamber to heat the air in the drying chamber.

[0073] S7: Combustion air supply, which draws air from the garbage storage pit, heats it through the boiler system to form heated air, and then supplies it into S3 and S4;

[0074] Specifically, blower 301 draws cold air from the waste storage pit, heats it through heat exchanger 204 to form heated air, which then flows into the first air supply line 302 and the second air supply line 303. Part of the heated air is supplied to the combustion chamber 203 through the first air supply line 302 via the tertiary air vent 113 for the combustion of syngas. The other part of the heated air is supplied to the combustion chamber 109 through the second air supply line 303 to provide oxygen for combustion in the combustion chamber 109.

[0075] S8: Exhaust gas treatment, low-temperature flue gas is introduced into flue gas purification system 5, and after desulfurization, activated carbon adsorption and dust removal, it is introduced into the chimney for emission in compliance with standards;

[0076] Specifically, the heat exchange flue gas temperature is 220-250℃, which is then passed into the gas scrubbing tower 501 for desulfurization and activated carbon adsorption treatment. In this application, desulfurization agents, including lime slurry, are used for desulfurization. Activated carbon is used for adsorption treatment to remove harmful gases such as dioxins and SOx present in the flue gas. After adsorption, the heat exchange flue gas enters a dust collector for dust removal. In this application, the dust collector is a bag filter 502, and the fly ash generated during dust removal is conveyed to the second fly ash treatment 507. After dust removal, the flue gas meets the emission standards, and the generated low-temperature flue gas is drawn out for emission.

[0077] S9: Low-temperature flue gas circulation, extracting low-temperature flue gas from the end of flue gas purification system 5 and supplying it into S1 and S2 respectively; the low-temperature flue gas is supplied into S1 in the form of direct supply and mixed supply, wherein the mixed supply is to mix low-temperature flue gas with high-temperature flue gas to form circulating mixed flue gas before supplying it, and the temperature of the circulating mixed flue gas is distributed in a gradient.

[0078] Specifically, the low-temperature exhaust fan 410 draws low-temperature flue gas between the induced draft fan 503 and the chimney 504, and then introduces it into the first flue gas duct 401 via the second flue gas duct 402. After passing through the first flue gas duct 401, the low-temperature flue gas is divided into three paths, which are as follows according to the flue gas flow direction: through the fifth manifold 407 into the gasification chamber 108 below the side beam of the integrated grate body 106, to protect the side beam; through the third manifold 405 into the drying chamber 107, where it mixes with the high-temperature flue gas in the second manifold 404 before being supplied, forming a gradient circulating mixed flue gas, which is then supplied to the area below the moving section of the integrated grate body 106 in the drying chamber 107 for gradient drying; and through the fourth manifold 406 into the drying chamber 107 below the side beam of the integrated grate body 106, to protect the side beam.

[0079] The above are merely embodiments of the present invention, and the invention is not limited to the fields covered by these embodiments. Commonly known structures and characteristics in the solutions are not described in detail here. It should be noted that those skilled in the art can make various modifications and improvements without departing from the structure of the present invention, and these should also be considered within the scope of protection of the present invention. These modifications and improvements will not affect the effectiveness of the present invention or the practicality of the patent. The scope of protection claimed in this application should be determined by the content of its claims, and the specific embodiments described in the specification can be used to interpret the content of the claims.

Claims

1. An integrated grate-type waste gasification combustion method, characterized by, Includes the following steps: S1: Drying, gradient temperature drying, after the waste is dried, dry flue gas and dry waste are produced; S2: Pyrolysis gasification, which pyrolyzes and gasifies the dried waste to produce bottom ash and pyrolysis gasification synthesis flue gas. The dried flue gas is fed into the gasifier to mix and reform the synthesis flue gas. S3: Combustion, the bottom ash is combusted at high temperature, producing ash and flue gas; the ash is utilized for resource recovery, and the flue gas is returned to be mixed and reformed with pyrolysis gasification synthesis flue gas and dried flue gas. S4: Syngas combustion, which involves secondary high-temperature combustion of the reformed pyrolysis gasification synthesis flue gas to produce high-temperature flue gas, while simultaneously performing high-temperature denitrification; S5: Waste heat recovery and utilization, high-temperature flue gas passes through the boiler system and heat exchanger to generate low-temperature flue gas, water steam, and heat the air; S6: High-temperature flue gas circulation, extracting high-temperature flue gas from the boiler system and supplying it into S1, S2 and S4 respectively; S7: Combustion air supply, which draws air from the garbage storage pit, heats it through the boiler system to form heated air, and then supplies it into S3 and S4; S8: Exhaust gas treatment. Low-temperature flue gas is introduced into the exhaust gas treatment system and undergoes desulfurization, activated carbon adsorption and dust removal in sequence before being introduced into the chimney for emission in compliance with standards. S9: Low-temperature flue gas circulation, low-temperature flue gas is extracted from the end of the flue gas purification system and supplied to S1 and S2 respectively; the low-temperature flue gas is supplied to S1 in the following ways: direct supply and mixed supply. The mixed supply is to mix the low-temperature flue gas with the high-temperature flue gas to form a circulating mixed flue gas before supplying it. The temperature of the circulating mixed flue gas is distributed in a gradient.

2. The integrated grate gasification combustion method according to claim 1, characterized in that: The high-temperature flue gas temperature in S6 is 500-550℃; the heating air temperature in S7 is 100-150℃; the low-temperature flue gas temperature in S9 is 120-150℃; and the circulating mixed flue gas temperatures are 180-250℃, 250-300℃, and 300-350℃, respectively.

3. The integrated grate gasification combustion method according to claim 2, characterized in that: The oxygen content of the high-temperature flue gas in S6 is 6%-10%; the oxygen content of the heated air is 21%; and the oxygen content of the low-temperature flue gas is 8%-12%.

4. The integrated grate gasification combustion method according to claim 1, characterized in that: The drying temperature in S1 is 150-500℃, and the drying flue gas temperature is 450-500℃.

5. The integrated grate gasification combustion method according to claim 1, characterized in that: The pyrolysis gasification combustion temperature in S2 is 500-850℃, and the burnout temperature in S3 is 850-950℃.

6. The integrated grate gasification combustion method according to claim 1, characterized in that: The pyrolysis gasification synthesis flue gas from reforming in S4 contains 10-15% nitric oxide, 5-8% hydrogen, and 5-8% methane, and the secondary high-temperature combustion temperature is 900-1050℃.

7. The integrated grate-type waste gasification and combustion method according to claim 1, characterized in that: The S6 also includes high-temperature dust removal at 600-650℃, and the high-temperature flue gas after dust removal is supplied to S1, S2 and S4 respectively.

8. The integrated grate-type waste gasification and combustion method according to claim 1, characterized in that: The S8 has a low-temperature flue gas temperature of 220-250℃, a desulfurization temperature of 220-250℃, a dust removal temperature of 180-220℃, and a chimney emission temperature of 150-180℃.

9. An integrated grate waste gasification combustion system implementing the method of any one of claims 1-8, characterized in that: The system includes a gasification combustion furnace for waste drying and gasification; a combustion chamber for combustion of gasification synthesis flue gas; a boiler system for waste heat recovery and utilization; a flue gas purification system for treating flue gas; an air supply system for providing external air to the system; and a flue gas circulation system for internal circulation of flue gas within the system. The gasification combustion system, boiler system, and exhaust gas treatment system are all equipped with flue gas inlets and outlets. The flue gas outlet of the gasification combustion furnace is connected to the flue gas inlet of the boiler system, and the flue gas outlet of the boiler system is connected to the flue gas inlet of the exhaust gas treatment system. The gasification combustion furnace is equipped with an integrated grate.

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