A combined cycle fluidized bed boiler

Abstract

The utility model discloses a kind of mixed combustion circulating fluidized bed boiler, it includes furnace, water-cooled cyclone separator and vertical flue connected in turn, the furnace interior is arranged with water-cooled screen, medium-temperature superheating screen and high-temperature superheating screen, the front of furnace is arranged with feeding system, the front side of furnace is arranged with multiple limestone interfaces, the both sides of furnace are arranged with multiple dry gas interfaces, the furnace outlet is arranged with SNCR deactivation system, the bottom of water-cooled cyclone separator is arranged with back material system communicated with the furnace;Low-temperature superheater, high-temperature economizer, SCR deactivation system, low-temperature economizer and air preheater are sequentially arranged from top to bottom in the vertical flue.The utility model can realize coal, sludge, petroleum coke, biomass, dry gas mixed combustion, simultaneously using limestone spray in boiler to carry out desulfurization treatment, using SNCR deactivation system and SCR deactivation system to carry out deactivation treatment, while resource energy recovery, also reduce environmental pollution.

Description

Technical Field

[0001] This utility model relates to the field of circulating fluidized bed boiler technology, specifically to a co-firing circulating fluidized bed boiler. Background Technology

[0002] Circulating fluidized bed combustion (CFBCC) is a highly efficient and low-pollution clean coal combustion technology. Its main characteristic is that the boiler furnace contains a large amount of material. During combustion, a significant amount of material is carried by the flue gas to the upper part of the furnace. A separator located at the furnace outlet separates the material from the flue gas, and the material is then returned to the bed via a non-mechanical return valve for multiple cycles of combustion. Due to the high material concentration, large heat capacity, and good mixing, these circulating materials result in a high heat transfer coefficient, enabling the boiler to have a wide range of heat load adjustment and strong adaptability to different fuels.

[0003] With the rapid development of my country's economy, a large amount of sludge, petroleum coke, dry gas, biomass and other materials have been generated. These materials have low utilization value, are difficult to treat, and will pollute the environment. Therefore, how to rationally utilize these materials without polluting the environment and also achieve resource and energy recovery is a problem that urgently needs to be solved by those skilled in the art. Utility Model Content

[0004] The purpose of this invention is to provide a co-firing circulating fluidized bed boiler to solve the problems mentioned in the background art.

[0005] To solve the above-mentioned technical problems, this utility model provides a co-fired circulating fluidized bed boiler, which includes a furnace, a water-cooled cyclone separator, and a vertical flue connected in sequence. The furnace is equipped with a water-cooled screen, a medium-temperature superheater, and a high-temperature superheater. A feeding system is arranged in front of the furnace. Multiple limestone inlets are arranged on the front side of the furnace. Multiple dry gas inlets are arranged on both sides of the furnace. An SNCR denitrification system is arranged at the furnace outlet. A return system connected to the furnace is arranged at the bottom of the water-cooled cyclone separator. A low-temperature superheater, a high-temperature economizer, an SCR denitrification system, a low-temperature economizer, and an air preheater are arranged in sequence from top to bottom in the vertical flue.

[0006] Furthermore, the furnace chamber is enclosed by a membrane water-cooled wall.

[0007] Furthermore, the water-cooled cyclone separator is formed by a membrane water-cooled wall.

[0008] Furthermore, the top of the water-cooled cyclone separator is connected to the vertical flue via a connecting flue.

[0009] Furthermore, the material return system adopts a "U"-shaped material return device.

[0010] Furthermore, the water-cooled screen is arranged in the center of the furnace, the high-temperature superheated screen is arranged on both sides of the water-cooled screen, and the medium-temperature superheated screen is arranged outside the high-temperature superheated screen.

[0011] Furthermore, the number of water-cooled cyclone separators is two.

[0012] The beneficial effects of this utility model are as follows: This utility model allows coal, sludge, petroleum coke, and biomass to enter the furnace for combustion through the feeding system, and dry gas enters the furnace for combustion through the dry gas interface, which can realize the co-firing of coal, sludge, petroleum coke, biomass, and dry gas. At the same time, limestone is sprayed in the boiler for desulfurization treatment, and SNCR denitrification system and SCR denitrification system are used for denitrification treatment. While recovering resources and energy, it also reduces environmental pollution. Attached Figure Description

[0013] Figure 1 This is a schematic diagram of the elevation structure of an embodiment of the present utility model.

[0014] Figure 2 This is a top view of an embodiment of the present invention.

[0015] The components include: 1. Furnace; 2. Water-cooled cyclone separator; 3. Vertical flue; 4. Feeding system; 5. Return system; 6. Water-cooled screen; 7. Medium-temperature superheater screen; 8. High-temperature superheater screen; 9. Connecting flue; 10. Low-temperature superheater; 11. High-temperature economizer; 12. Low-temperature economizer; 13. Air preheater; 14. Dry gas interface; 15. SNCR denitrification system; 16. SCR denitrification system; 17. Limestone interface. Detailed Implementation

[0016] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only one embodiment of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.

[0017] To make the objectives, technical solutions and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and specific embodiments.

[0018] In the following description, references to "an embodiment," "an embodiment," "an example," "example," etc., indicate that the described embodiment or example may include a particular feature, structure, characteristic, property, element, or limitation, but not every embodiment or example necessarily includes that particular feature, structure, characteristic, property, element, or limitation. Furthermore, the repeated use of the phrase "an embodiment according to this application," while possibly referring to the same embodiment, does not necessarily refer to the same embodiment.

[0019] like Figures 1-2 As shown, this utility model discloses a co-firing circulating fluidized bed boiler, which includes a furnace 1, a water-cooled cyclone separator 2 and a vertical flue 3 connected in sequence. The furnace 1 is equipped with a water-cooled screen 6, a medium-temperature superheater screen 7 and a high-temperature superheater screen 8. A feeding system 4 is arranged in front of the furnace 1. Multiple limestone inlets 17 are arranged on the front side of the furnace 1. Multiple dry gas inlets 14 are arranged on both sides of the furnace 1. An SNCR denitrification system 15 is arranged at the outlet of the furnace 1. A return material system 5 connected to the furnace 1 is arranged at the bottom of the water-cooled cyclone separator 2. A low-temperature superheater 10, a high-temperature economizer 11, an SCR denitrification system 16, a low-temperature economizer 12 and an air preheater 13 are arranged in sequence from top to bottom in the vertical flue 3.

[0020] Solid fuels (coal, sludge, petroleum coke, biomass) are fed into the high-temperature bed material zone at the bottom of the furnace 1 through the feeding system 4 in front of the furnace 1, while gaseous fuels (dry gas) are directly injected into the combustion zone of the furnace 1 through multiple dry gas ports 14 on both sides of the furnace 1 for combustion.

[0021] The high-temperature flue gas produced by combustion, along with the entrained fine solid particles (unburned carbon, ash, limestone, etc.), flows upward through the furnace 1. During the ascent, the flue gas undergoes intense radiative and convective heat exchange with the water-cooled screen 6, the medium-temperature superheated screen 7, and the high-temperature superheated screen 8 arranged within the furnace 1, generating high-temperature, high-pressure steam for power generation.

[0022] Subsequently, the gas-solid mixture enters the water-cooled cyclone separator 2 from the outlet of furnace 1. Under centrifugal force, most of the coarse solid particles are separated, while the clean flue gas is discharged from the top of the water-cooled cyclone separator 2 into the vertical flue 3. The separated high-temperature solid particles are continuously and stably transported back to the bottom of furnace 1 through the return system 5 at the bottom of the water-cooled cyclone separator 2. This allows unburned fuel particles to return to the combustion zone multiple times, providing sufficient time for complete combustion and improving combustion efficiency. At the same time, the high-temperature circulating ash carries heat back to furnace 1, helping to preheat and dry newly entered fuel (especially wet sludge), stabilizing the furnace temperature, and ensuring extremely high heat transfer efficiency within furnace 1.

[0023] Within the vertical flue 3, the flue gas flows sequentially through the low-temperature superheater 10 (for further heating the steam), the high-temperature economizer 11 and the low-temperature economizer 12 (for heating boiler feedwater, recovering waste heat from the flue gas, and improving boiler efficiency), the SCR denitrification system (where a reducing agent is injected to deeply reduce nitrogen oxides (NOx) generated in the flue gas within the furnace 1 into harmless nitrogen and water under the action of a catalyst), and the air preheater 13 (which utilizes the waste heat of the flue gas to preheat the combustion air entering the furnace 1, improving combustion efficiency and reducing exhaust losses). This maximizes the recovery of heat from the flue gas, maintaining the overall thermal efficiency of the boiler at a high level.

[0024] Simultaneously, during combustion, limestone (mainly CaCO3) is injected into the furnace through the limestone inlet 17 at the front of the furnace chamber 1. The limestone decomposes into CaO at high temperature, which reacts with SO2 produced by fuel combustion to generate CaSO4 (gypsum), thus achieving dry desulfurization in the furnace.

[0025] An SNCR denitrification system 15 is arranged at the outlet of furnace 1. Specifically, multiple SNCR denitrification system 15 interfaces are arranged. An amino reducing agent (such as ammonia or urea) is injected through the SNCR denitrification system 15 interfaces to reduce part of the NOx under high temperature and catalyst-free conditions.

[0026] In the intermediate temperature zone of vertical flue 3, deep denitrification is achieved through an SCR system with the aid of a catalyst, resulting in ultra-low NOx emissions. This constructs a comprehensive pollutant control system covering the entire process from combustion to post-combustion, reducing environmental pollution.

[0027] This invention uses a feeding system 4 to allow coal, sludge, petroleum coke, and biomass to enter the furnace 1 for combustion, while dry gas enters the furnace 1 through a dry gas inlet 14 for combustion. This enables the co-firing of coal, sludge, petroleum coke, biomass, and dry gas. At the same time, limestone is sprayed into the boiler for desulfurization, and SNCR denitrification system 15 and SCR denitrification system 16 are used for denitrification. This not only recovers resources and energy but also reduces environmental pollution.

[0028] In one embodiment, the furnace chamber 1 is enclosed by a membrane water-cooled wall.

[0029] In one embodiment, the water-cooled cyclone separator 2 is enclosed by a membrane water-cooled wall.

[0030] In one embodiment, the top of the water-cooled cyclone separator 2 is connected to the vertical flue 3 via a connecting flue 9.

[0031] In one embodiment, the return system 5 employs a U-shaped return feeder. Its vertical section is connected to the bottom of the water-cooled cyclone separator 2 and is used to store the separated high-temperature circulating ash. Specifically, the high-temperature ash separated from the water-cooled cyclone separator 2 falls into and fills the riser by gravity, forming a "material column" of a certain height. Its inclined section returns the material to the furnace 1.

[0032] In one embodiment, the water-cooled screen 6 is arranged in the center of the furnace 1, the high-temperature superheated screen 8 is arranged on both sides of the water-cooled screen 6, and the medium-temperature superheated screen 7 is arranged outside the high-temperature superheated screen 8. The specific arrangement of the water-cooled screen 6, the high-temperature superheated screen 8, and the medium-temperature superheated screen 7 in the furnace 1 realizes the cascade utilization of heat.

[0033] The furnace 1 is divided into a core zone: a water-cooled screen 6, which absorbs the radiant heat from the high-temperature flames and flue gas within the furnace 1, causing the water inside the tubes to evaporate into steam. This also reduces localized high temperatures within the furnace 1, preventing coking on the furnace walls and protecting the furnace structure. The intermediate zone: a high-temperature superheated screen 8, which further absorbs the high-temperature heat from the furnace 1, heating the saturated steam into high-temperature superheated steam, increasing the steam temperature and work capacity to meet different process requirements. The outer zone: a medium-temperature superheated screen 7, which absorbs relatively lower-temperature heat, further superheating the steam to make the steam temperature more uniform and stable, and also helps regulate the boiler's steam parameters.

[0034] In one embodiment, there are two water-cooled cyclone separators 2. Two return systems 5 are respectively arranged at the bottom of the two water-cooled cyclone separators 2, and the two flue gas outlets are respectively connected to two connecting flues 9, which converge into the vertical flue 3.

[0035] As boiler capacity increases, the cross-sectional area of ​​the furnace 1 also increases. A single water-cooled cyclone separator 2 may not be able to handle all the flue gas, or its diameter may become too large to be designed and manufactured. Therefore, using two parallel water-cooled cyclone separators 2 is a standard and reasonable design choice to meet the processing requirements of large flue gas volumes. This ensures that the vast majority of highly reactive circulating material carrying unburned carbon particles and unreacted limestone can be efficiently captured and fed into the water-cooled cyclone separator 2, thereby achieving optimal circulating combustion and desulfurization effects.

[0036] The above description of the disclosed embodiments enables those skilled in the art to implement or use this invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, this invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A co-firing circulating fluidized bed boiler, characterized in that: The system includes a furnace, a water-cooled cyclone separator, and a vertical flue connected in sequence. Inside the furnace, there are water-cooled screens, medium-temperature superheaters, and high-temperature superheaters. A feeding system is located in front of the furnace, and multiple limestone inlets are located on the front side of the furnace. Multiple dry gas inlets are located on both sides of the furnace. An SNCR denitrification system is located at the furnace outlet. A return system connected to the furnace is located at the bottom of the water-cooled cyclone separator. Inside the vertical flue, from top to bottom, there are a low-temperature superheater, a high-temperature economizer, an SCR denitrification system, a low-temperature economizer, and an air preheater.

2. The co-firing circulating fluidized bed boiler according to claim 1, characterized in that: The furnace chamber is enclosed by a membrane water-cooled wall.

3. A co-firing circulating fluidized bed boiler according to claim 1, characterized in that: The water-cooled cyclone separator is composed of membrane water-cooled walls.

4. A co-firing circulating fluidized bed boiler according to claim 1, characterized in that: The top of the water-cooled cyclone separator is connected to the vertical flue via a connecting flue.

5. A co-firing circulating fluidized bed boiler according to claim 1, characterized in that: The material return system adopts a "U"-shaped material return device.

6. A co-firing circulating fluidized bed boiler according to claim 1, characterized in that: The water-cooled screen is arranged in the center of the furnace, the high-temperature superheated screen is arranged on both sides of the water-cooled screen, and the medium-temperature superheated screen is arranged outside the high-temperature superheated screen.

7. A co-firing circulating fluidized bed boiler according to claim 6, characterized in that: The number of water-cooled cyclone separators is two.

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