A garbage incineration system with flue gas external combustion bypass and its process

Abstract

The present invention discloses a garbage incineration system with a flue gas external combustion bypass and a process thereof, comprising a flue gas external combustion bypass, a grate-type incinerator, a main flue gas waste heat recovery device and a steam power generation device. The flue gas external combustion bypass is provided with a bypass flue gas inlet, a bypass flue gas outlet, a steam inlet and a steam outlet. The bypass flue gas inlet and the bypass flue gas outlet are both connected to the grate-type incinerator to form a circulation loop. The steam inlet is connected to the main flue gas waste heat recovery device, the steam outlet is connected to the steam power generation device, and the grate-type incinerator is connected to the main flue gas waste heat recovery device. The present invention avoids problems such as excessive combustion temperature caused by excessive calorific value of garbage. After the extracted bypass flue gas is burned in the flue gas external combustion bypass, it can be used to further improve the steam parameters in the terminal superheater, thereby achieving the purpose of improving power generation efficiency while not affecting the processing capacity when using an existing incinerator to treat high calorific value garbage.

Description

Technical Field

[0001] The present invention relates to a garbage incineration system and a process thereof, in particular to a garbage incineration system and a process thereof with a flue gas external combustion bypass, belonging to the technical field of solid waste treatment. Background Art

[0002] With the institutionalization and widespread adoption of waste sorting in my country, the feedstock entering waste incinerators will gradually shift from a mix of household waste to primarily dry waste. This significantly increases the calorific value of waste compared to mixed waste, placing a significant strain on existing incineration processes and equipment. Currently, incinerators are often designed based on the design calorific value at the maximum waste capacity (MCR) point. When the calorific value of waste exceeds the design calorific value, the waste capacity must be reduced to maintain a constant heat load to ensure safe and stable operation. Otherwise, the furnace temperature will rise significantly, increasing the boiler's heat load and causing excessively high flue gas temperatures at the incinerator outlet, which can easily lead to coking, ash blockage, and high-temperature corrosion on subsequent heating surfaces. Therefore, as the calorific value of waste increases, existing waste incinerators often struggle to meet their full capacity requirements to ensure the safety of the incineration process. This not only results in low operational efficiency but also eliminates the opportunity to increase steam parameters and thus power generation efficiency by burning high-calorific waste. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a garbage incineration system with a flue gas external combustion bypass and a process thereof, so as to realize the use of an existing incinerator to treat high calorific value garbage without affecting the processing capacity and improving the steam parameters.

[0004] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0005] A waste incineration system with an external flue gas combustion bypass is characterized in that it includes an external flue gas combustion bypass, a grate incinerator, a main flue gas waste heat recovery device and a steam power generation device. The external flue gas combustion bypass is provided with a bypass flue gas inlet, a bypass flue gas outlet, a steam inlet and a steam outlet. The bypass flue gas inlet and the bypass flue gas outlet are both connected to the grate incinerator to form a circulation loop. The steam inlet is connected to the main flue gas waste heat recovery device, the steam outlet is connected to the steam power generation device, and the grate incinerator is connected to the main flue gas waste heat recovery device.

[0006] Furthermore, the flue gas external combustion bypass includes an air preheater, an external flue gas purifier, an external combustion chamber and an external superheater, the flue gas inlet of the air preheater is connected to the grate incinerator, the flue gas outlet of the air preheater is connected to one end of the external flue gas purifier, the normal temperature clean air inlet of the air preheater is passed through the normal temperature clean air, the preheated air outlet of the air preheater is connected to the air inlet of the external combustion chamber, the other end of the external flue gas purifier is connected to the flue gas inlet of the external combustion chamber, the flue gas outlet of the external combustion chamber is connected to the flue gas inlet of the external superheater, the flue gas outlet of the external superheater is connected to the grate incinerator, the steam inlet of the external superheater is connected to the steam outlet of the main flue gas waste heat recovery device, and the steam outlet of the external superheater is connected to the steam inlet of the steam power generation device.

[0007] Furthermore, the air preheater is a tubular heat exchanger, clean air at room temperature flows through the tube side, and bypass flue gas flows through the shell side, and the heat exchange tube material is made of high temperature and corrosion resistant silicon carbide ceramics.

[0008] Furthermore, the external flue gas purifier consists of a hot gas filter and a dry adsorption chamber.

[0009] Furthermore, the external combustion chamber is arranged as a membrane water-cooled wall, the outer wall of the water-cooled wall metal tube adopts Inconel625 full cladding, the cladding thickness is 2-3 mm, and a preheating air nozzle is provided in the external combustion chamber, and the preheating air nozzle is connected to the air inlet of the external combustion chamber.

[0010] Furthermore, the furnace wall of the exhaust gas combustion section of the grate-type incinerator is provided with a bypass exhaust port, multiple bypass exhaust ports are evenly arranged on the furnace wall and each bypass exhaust port is individually controlled by an independent valve, the bypass exhaust port is connected to the bypass flue gas inlet of the flue gas external combustion bypass, and the bypass exhaust port is located 0.5 meters above the top height of the material layer.

[0011] Furthermore, a bypass flue gas recirculation nozzle is provided on the side wall of the secondary combustion chamber of the grate-type incinerator, and the bypass flue gas recirculation nozzle is located below the secondary air nozzle of the secondary combustion chamber.

[0012] Furthermore, the main flue gas waste heat recovery device includes a pre-evaporator, a three-stage superheater, a two-stage evaporator, and a two-stage economizer, and the pre-evaporator, the three-stage superheater, the two-stage evaporator, and the two-stage economizer are arranged in sequence along the flue gas flow direction.

[0013] Furthermore, the three-stage superheater includes a high-temperature superheater, a medium-temperature superheater and a low-temperature superheater, wherein the high-temperature superheater adopts downstream flow, the medium-temperature superheater adopts mixed flow or countercurrent flow, and the low-temperature superheater adopts countercurrent flow.

[0014] A waste incineration process of a waste incineration system with a flue gas external combustion bypass is characterized by comprising the following steps:

[0015] S1. Extract the high-temperature flue gas in the exhaust combustion section of the grate-type incinerator through the bypass exhaust port and send it to the flue gas external combustion bypass;

[0016] S2. The bypass flue gas exchanges heat with clean air at room temperature in the air preheater. The bypass flue gas is cooled to 400±25℃. At this temperature, the volatile alkali metals and heavy metal chlorides contained in the bypass flue gas are converted from gaseous state to solid state and precipitated. At the same time, the clean air at room temperature is heated to 350±50℃.

[0017] S3. The cooled bypass flue gas enters the external flue gas purifier to remove entrained solid particles and acidic components;

[0018] S4, the purified bypass flue gas enters the external combustion chamber, and the preheated air generated in step S2 is injected into the external combustion chamber, and the flue gas is completely burned under a condition of slightly excess air;

[0019] S5. The high-temperature flue gas generated after combustion enters the external superheater, which continues to heat the steam from the main flue gas waste heat recovery device while maintaining the steam pressure constant; then, the high-temperature superheated steam enters the steam power generation device to generate electricity;

[0020] S6. The flue gas after heat exchange in the external superheater enters the secondary combustion chamber of the grate-type incinerator through the bypass flue gas recirculation nozzle, and is fully mixed with the main flue gas to complete the external flue gas circulation.

[0021] Compared with the prior art, the present invention has the following advantages and effects:

[0022] 1. The present invention is suitable for the treatment of high-calorific-value waste after the transformation of existing grate-type waste incineration facilities. By extracting some incompletely burned flue gas from the exhaust combustion section of the furnace, it avoids the risk of excessive combustion temperature in the secondary combustion chamber, excessive flue gas volume, and subsequent overload operation caused by excessive combustible components entering the secondary combustion chamber. This ensures the safety of the production process without reducing the processing capacity of the waste incineration facility.

[0023] 2. The present invention can improve power generation efficiency. By providing an external flue gas combustion bypass, the diverted high-calorific value flue gas is burned and the steam generated in the main flue gas waste heat recovery device is reheated, thereby improving the steam parameters of the existing facility and thus improving power generation efficiency.

[0024] 3. The present invention can reduce the secondary air supply; the flue gas after heat exchange in the external superheater is recirculated and enters the secondary combustion zone through the incinerator bypass flue gas recirculation nozzle, which can reduce the demand for secondary air in the secondary combustion chamber of the grate type incinerator;

[0025] 4. When using the present invention to transform existing grate-type waste incineration facilities, there is no need to dismantle and rebuild the existing grate-type incinerator, flue gas waste heat recovery device, etc., nor is there any need to make major changes to the layout of existing equipment. Therefore, the transformation cost is low and the economic benefit is good. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a schematic diagram of a waste incineration system with a flue gas external combustion bypass according to the present invention.

[0027] Figure 2 Schematic diagram of the flue gas external combustion bypass of the present invention. DETAILED DESCRIPTION

[0028] In order to elaborate on the technical solutions adopted by the present invention to achieve the predetermined technical purpose, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments, and the technical means or technical features in the embodiments of the present invention can be replaced without creative work. The present invention will be described in detail below with reference to the drawings and in conjunction with the embodiments.

[0029] like Figure 1 As shown, the waste incineration system with an external flue gas combustion bypass of the present invention comprises an external flue gas combustion bypass 1, a grate-type incinerator 2, a main flue gas waste heat recovery device 3, and a steam power generation device 4. The external flue gas combustion bypass 1 is provided with a bypass flue gas inlet 5, a bypass flue gas outlet 6, a steam inlet 7, and a steam outlet 8. The bypass flue gas inlet 5 and the bypass flue gas outlet 6 are both connected to the grate-type incinerator 2 to form a circulation loop. After the flue gas entering the external flue gas combustion bypass 1 undergoes processes such as cooling, purification, combustion, and heat exchange, it passes through the bypass flue gas outlet 6 and is returned to the secondary combustion chamber of the grate-type incinerator through a bypass flue gas recirculation nozzle provided in the grate-type incinerator, thus forming a complete external flue gas circulation loop. The steam inlet 7 is connected to the main flue gas waste heat recovery device 3, the steam outlet 8 is connected to the steam power generation device 4, and the grate-type incinerator 2 is connected to the main flue gas waste heat recovery device 3. When the calorific value of the garbage in the grate-type incinerator 2 is too high, causing the furnace temperature to exceed the set value, the flue gas external combustion bypass 1 extracts the unburned flue gas in the furnace for bypass combustion. The heat generated by the bypass combustion secondary heats the steam generated by the main flue gas waste heat recovery device 3, thereby increasing the calorific value of the steam. The flue gas generated by the bypass combustion is then returned to the grate-type incinerator 2. The steam generated by the main flue gas waste heat recovery device 3 is fed into the external superheater in the flue gas external combustion bypass 1 through the steam inlet 7. After further heating, it is fed into the steam power generation device 4 through the steam outlet 8 to generate electricity.

[0030] like Figure 2As shown, the flue gas external combustion bypass 1 includes an air preheater 9, an external flue gas purifier 10, an external combustion chamber 11 and an external superheater 12. The flue gas inlet of the air preheater 9 is connected to the grate incinerator 2. The flue gas inlet of the air preheater 9 is also the bypass flue gas inlet 5 of the flue gas external combustion bypass 1. The flue gas outlet 13 of the air preheater 9 is connected to one end of the external flue gas purifier 10, and the normal temperature clean air inlet 14 of the air preheater 9 is connected to the normal temperature clean air. The preheated air outlet 15 of the air preheater 9 is connected to the air inlet 16 of the external combustion chamber 11, and the other end of the external flue gas purifier 10 is connected to the flue gas inlet 17 of the external combustion chamber 11. The flue gas outlet 18 of the external combustion chamber 11 is connected to the flue gas inlet 19 of the external superheater 12. The flue gas outlet of the external superheater 12 (i.e., the bypass flue gas outlet 6 of the flue gas external combustion bypass 1) is connected to the grate incinerator 2, the steam inlet of the external superheater 12 (i.e., the steam inlet 7 of the flue gas external combustion bypass 1) is connected to the steam outlet of the main flue gas waste heat recovery device 3, and the steam outlet of the external superheater 12 (i.e., the steam outlet 8 of the flue gas external combustion bypass 1) is connected to the steam inlet of the steam power generation device 4.

[0031] The air preheater 9 is a tubular heat exchanger, with clean air at room temperature flowing through the tube side and bypass flue gas flowing through the shell side. The heat exchange tubes are made of high-temperature and corrosion-resistant silicon carbide ceramic. The external flue gas purifier 10 consists of a hot gas filter for filtering solid particulate matter and a dry adsorption chamber for adsorbing chlorides and sulfides. The external combustion chamber 11 features a membrane-type water-cooled wall arrangement. The outer wall of the water-cooled wall metal tubes is fully clad with Inconel 625, with a thickness of 2-3 mm. A preheating air nozzle is installed within the external combustion chamber 11 and is connected to the air inlet of the external combustion chamber.

[0032] The furnace wall of the gasification combustion section of the grate-type incinerator 2 is provided with a bypass exhaust port 20 for extracting part of the flue gas generated by the pyrolysis and incomplete combustion of the garbage and sending it to the flue gas external combustion bypass 1. Multiple bypass exhaust ports 20 are evenly arranged on the furnace wall and each bypass exhaust port is individually controlled by an independent valve. The bypass exhaust port 20 is connected to the bypass flue gas inlet 5 of the flue gas external combustion bypass 1. The bypass exhaust port 20 is located 0.5 meters above the top of the material layer. It extracts the incomplete combustion flue gas rich in high calorific value and low corrosive components from the gasification combustion section and sends it to the flue gas external combustion bypass 1. The side wall of the secondary combustion chamber of the grate-type incinerator 2 is provided with a bypass flue gas recirculation nozzle 21, which is located below the secondary air nozzle of the secondary combustion chamber. The high-temperature flue gas discharged from the external combustion chamber 11 enters the external superheater 12, reheats the steam, and is then sent into the grate incinerator 2 through the bypass flue gas recirculation nozzle 21 installed downstream of the secondary air nozzle in the second combustion chamber to promote sufficient mixing of the bypass flue gas and the main flue gas.

[0033] The main flue gas waste heat recovery device 3 comprises a pre-evaporator, a third-stage superheater, a second-stage evaporator, and a second-stage economizer, all arranged sequentially along the flue gas flow. The third-stage superheater comprises a high-temperature superheater, a medium-temperature superheater, and a low-temperature superheater. The high-temperature superheater utilizes a forward flow system, the medium-temperature superheater utilizes a mixed flow or counterflow system, and the low-temperature superheater utilizes a counterflow system, effectively reducing the flue gas inlet temperature.

[0034] A waste incineration process of a waste incineration system with a flue gas external combustion bypass comprises the following steps:

[0035] S1. Extract the high-temperature flue gas in the exhaust combustion section of the grate-type incinerator through the bypass exhaust port and send it to the flue gas external combustion bypass;

[0036] S2. The bypass flue gas exchanges heat with clean air at room temperature in the air preheater. The bypass flue gas is cooled to 400±25℃. At this temperature, the volatile alkali metals and heavy metal chlorides contained in the bypass flue gas are converted from gaseous state to solid state and precipitated. At the same time, the clean air at room temperature is heated to 350±50℃.

[0037] S3. The cooled bypass flue gas enters the external flue gas purifier to remove entrained solid particles and acidic components;

[0038] S4, the purified bypass flue gas enters the external combustion chamber, and the preheated air generated in step S2 is injected into the external combustion chamber, and the flue gas is completely burned under a condition of slightly excess air;

[0039] S5. The high-temperature flue gas generated after combustion enters the external superheater, which continues to heat the steam from the main flue gas waste heat recovery device while maintaining the steam pressure constant; then, the high-temperature superheated steam enters the steam power generation device to generate electricity;

[0040] S6. The flue gas after heat exchange in the external superheater enters the secondary combustion chamber of the grate-type incinerator through the bypass flue gas recirculation nozzle, and is fully mixed with the main flue gas to complete the external flue gas circulation.

[0041] The present invention provides a waste incineration system with an external flue gas combustion bypass and a process thereof. By extracting part of the flue gas rich in combustible components generated in the exhaust combustion section of the grate-type incinerator for combustion, the system reduces the combustion intensity in the waste incinerator, thereby reducing the combustion temperature in the furnace and avoiding problems such as excessive combustion temperature caused by excessive calorific value of the waste. After the extracted bypass flue gas is burned in the external flue gas combustion bypass, it can be used to further improve the steam parameters in the terminal superheater, thereby achieving the goal of improving power generation efficiency while not affecting the processing capacity when using the existing incinerator to treat high calorific value waste.

[0042] The above description is merely a preferred embodiment of the present invention and does not constitute any form of limitation to the present invention. Although the present invention has been disclosed as a preferred embodiment as above, it is not intended to limit the present invention. Any technician familiar with the present profession can make some changes or modifications to equivalent embodiments of equivalent changes using the technical content disclosed above without departing from the scope of the technical solution of the present invention. However, any simple modification, equivalent replacement and improvement of the above embodiments made according to the technical essence of the present invention, within the spirit and principles of the present invention, without departing from the content of the technical solution of the present invention, shall still fall within the scope of protection of the technical solution of the present invention.

Claims

1. A waste incineration system with a flue gas external combustion bypass, characterized by: It includes a flue gas external combustion bypass, a grate-type incinerator, a main flue gas waste heat recovery device and a steam power generation device. The flue gas external combustion bypass is provided with a bypass flue gas inlet, a bypass flue gas outlet, a steam inlet and a steam outlet. The bypass flue gas inlet and the bypass flue gas outlet are both connected to the grate-type incinerator to form a circulation loop. The steam inlet is connected to the main flue gas waste heat recovery device, the steam outlet is connected to the steam power generation device, and the grate-type incinerator is connected to the main flue gas waste heat recovery device. The flue gas external combustion bypass comprises an air preheater, an external flue gas purifier, an external combustion chamber and an external superheater, the flue gas inlet of the air preheater is connected to the grate-type incinerator, the flue gas outlet of the air preheater is connected to one end of the external flue gas purifier, the normal temperature clean air inlet of the air preheater is connected to the air inlet of the external combustion chamber, the other end of the external flue gas purifier is connected to the flue gas inlet of the external combustion chamber, the flue gas outlet of the external combustion chamber is connected to the flue gas inlet of the external superheater, the flue gas outlet of the external superheater is connected to the grate-type incinerator, the steam inlet of the external superheater is connected to the steam outlet of the main flue gas waste heat recovery device, and the steam outlet of the external superheater is connected to the steam inlet of the steam power generation device; The furnace wall of the exhaust gas combustion section of the grate-type incinerator is provided with a bypass exhaust port, multiple bypass exhaust ports are evenly arranged on the furnace wall and each bypass exhaust port is individually controlled by an independent valve. The bypass exhaust port is connected to the bypass flue gas inlet of the flue gas external combustion bypass, and the bypass exhaust port is located 0.5 meters above the top of the material layer; A bypass flue gas recirculation nozzle is provided on the side wall of the secondary combustion chamber of the grate-type incinerator, and the bypass flue gas recirculation nozzle is located below the secondary air nozzle of the secondary combustion chamber.

2. The waste incineration system with flue gas external combustion bypass according to claim 1, characterized in that: The air preheater is a tubular heat exchanger, wherein clean air at room temperature flows through the tube side and bypass flue gas flows through the shell side. The heat exchange tube is made of high temperature resistant and corrosion resistant silicon carbide ceramic.

3. The waste incineration system with flue gas external combustion bypass according to claim 1, characterized in that: The external flue gas purifier consists of a hot gas filter and a dry adsorption chamber.

4. The waste incineration system with flue gas external combustion bypass according to claim 1, characterized in that: The external combustion chamber is arranged as a membrane water-cooled wall. The outer wall of the water-cooled wall metal tube adopts Inconel 625 full cladding with a cladding thickness of 2-3 mm. A preheating air nozzle is provided in the external combustion chamber and is connected to the air inlet of the external combustion chamber.

5. The waste incineration system with flue gas external combustion bypass according to claim 1, characterized in that: The main flue gas waste heat recovery device includes a pre-evaporator, a three-stage superheater, a two-stage evaporator, and a two-stage economizer. The pre-evaporator, the three-stage superheater, the two-stage evaporator, and the two-stage economizer are arranged in sequence along the flue gas flow direction.

6. The waste incineration system with flue gas external combustion bypass according to claim 5, characterized in that: The three-stage superheater includes a high-temperature superheater, a medium-temperature superheater and a low-temperature superheater, wherein the high-temperature superheater adopts downstream flow, the medium-temperature superheater adopts mixed flow or countercurrent flow, and the low-temperature superheater adopts countercurrent flow.

7. A waste incineration process of a waste incineration system with a flue gas external combustion bypass according to any one of claims 1 to 6, characterized in that The following steps are involved: S1. Extract the high-temperature flue gas in the exhaust combustion section of the grate-type incinerator through the bypass exhaust port and send it to the flue gas external combustion bypass; S2. The bypass flue gas exchanges heat with clean air at room temperature in the air preheater. The bypass flue gas is cooled to 400±25℃. At this temperature, the volatile alkali metals and heavy metal chlorides contained in the bypass flue gas are converted from gaseous state to solid state and precipitated. At the same time, the clean air at room temperature is heated to 350±50℃. S3. The cooled bypass flue gas enters the external flue gas purifier to remove entrained solid particles and acidic components; S4, the purified bypass flue gas enters the external combustion chamber, and the preheated air generated in step S2 is injected into the external combustion chamber, and the flue gas is completely burned under a condition of slightly excess air; S5. The high-temperature flue gas generated after combustion enters the external superheater, which continues to heat the steam from the main flue gas waste heat recovery device while maintaining the steam pressure constant; then, the high-temperature superheated steam enters the steam power generation device to generate electricity; S6. The flue gas after heat exchange in the external superheater enters the secondary combustion chamber of the grate-type incinerator through the bypass flue gas recirculation nozzle, and is fully mixed with the main flue gas to complete the external flue gas circulation.

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