High-alkali coal circulating fluidized bed boiler

Abstract

The utility model discloses a high-alkali coal circulating fluidized bed boiler which comprises a hearth, a cyclone separator, a cyclone separator outlet flue, a middle flue and a tail flue which are sequentially connected, and the lower end of the cyclone separator is connected with the hearth through a material returning device; a platen reheater and a high-temperature platen superheater are arranged in the hearth; a plurality of nozzles are arranged in an outlet flue of the cyclone separator; the middle flue is divided into a downstream flue and an upstream flue through a longitudinal water-cooling partition wall connected with the top of the middle flue, and water-cooling heat exchange tube bundles are arranged on the two side faces of the longitudinal water-cooling partition wall; a water cooling tube bundle is arranged in the upstream flue; the device can solve the problem of contamination and corrosion of the heating surface of the boiler, is suitable for coal types with different alkali metal contents, and realizes stable and efficient operation of pure combustion high-alkali coal.

Description

Technical Field

[0001] The utility model relates to a circulating fluidized bed boiler, in particular to a circulating fluidized bed boiler suitable for high-alkali coal. Background Art

[0002] The vast Gobi Desert stretching 220 kilometers from east to west in Xinjiang Zhundong Coalfield contains 390 billion tons of coal resources, which is very rich. According to my country's annual coal consumption, the Zhundong Coalfield alone is enough for the whole country to use for 100 years, which can provide a strong guarantee for my country's energy security. However, the overall content of Na2O and K2O in its coal ash is more than 6%, which is much higher than that of conventional power coal. The boiler will have serious contamination problems during the combustion process, which restricts the safe, efficient and clean use of Zhundong coal.

[0003] At present, in order to solve the contamination problem of burning high-alkali coal, patent CN212226992U discloses a circulating fluidized bed boiler structure with a cooling chamber for burning mixed fuels. A cooling chamber wall is set after the steam-cooled separator to reduce the flue gas temperature. A low-temperature superheater and a medium-temperature superheater are arranged in the cooling chamber wall, which can alleviate the alkali metal contamination and corrosion problem to a certain extent, but fails to completely solve the contamination problem caused by high-alkali fuel.

[0004] Another patent CN105805736B discloses a circulating fluidized bed boiler and a method for preventing the alkali metal compound contamination of its heating surface. The high-temperature evaporation heating surface is arranged at the tail flue to reduce the flue gas temperature, so that a small part of the alkali metal compounds in the flue gas solidifies into a solid state. However, the contamination blocks condensed on the wall are easy to fall and block on the tail heating surface, affecting the stable operation of the boiler. As a result, the existing circulating fluidized bed boiler burning high-alkali coal has not completely solved the contamination corrosion problem, affecting the long-term stable operation of the boiler. Summary of the invention

[0005] The purpose of the utility model is to provide a high-alkali coal circulating fluidized bed boiler in view of the above-mentioned deficiencies in the prior art, which can solve the problem of contamination and corrosion of the boiler heating surface, and is suitable for coals with different alkali metal contents, so as to achieve stable and efficient operation of pure high-alkali coal.

[0006] In order to achieve the above-mentioned purpose, the utility model provides a high-alkali coal circulating fluidized bed boiler, comprising a furnace, a cyclone separator, a cyclone separator outlet flue, an intermediate flue and a tail flue connected in sequence, wherein the lower end of the cyclone separator is connected to the furnace through a return device; the utility model is characterized in that: a screen reheater and a high-temperature screen superheater are arranged in the furnace; a plurality of nozzles are arranged in the cyclone separator outlet flue; the intermediate flue is divided into a descending flue and an ascending flue by a longitudinal water-cooled partition wall connected to the top thereof, and water-cooled heat exchange tube bundles are arranged on both sides of the longitudinal water-cooled partition wall; a water-cooled tube bundle is arranged in the ascending flue.

[0007] In use, the high-temperature platen superheater and the platen reheater are arranged in the furnace. By utilizing the scouring of a large amount of fluidized circulating materials in the furnace, corrosion caused by alkali metal contamination on the heating surface can be avoided. Several nozzles in the outlet flue of the cyclone separator can spray water or low-temperature steam to rapidly cool the high-temperature flue gas, providing a basis for the downstream heating surface to avoid the contamination-sensitive temperature range. The flue gas flows through the intermediate flue and simultaneously couples with the water-cooled tube bundle through the longitudinal water-cooled partition wall to further cool the flue gas, causing the alkali metal compounds therein to cool and solidify into a solid state, thoroughly solving the problem of contamination and corrosion of the heating surface at the boiler tail. It can be applied to coal types with different alkali metal contents, realizing the stable and efficient operation of burning high-alkali coal purely;

[0008] As a further improvement of the present utility model, the side walls of the downcomer flue and the upcomer flue are both steam-cooled casings, and steam heat exchange tube bundles are provided on both steam-cooled casings; the flue gas can be further cooled. Even when burning coal with a high alkali metal content, the downstream heating surface can be made to avoid the contamination-sensitive temperature range and prevent contamination and corrosion;

[0009] As a further improvement of the present utility model, the several nozzles are arranged symmetrically in groups of two in the outlet flue of the cyclone separator; the cooling effect on the high-temperature flue gas can be improved;

[0010] As a further improvement of the present utility model, a medium-temperature superheater and a low-temperature superheater are arranged in sequence in the upcomer flue behind the water-cooled tube bundle; heat exchange with the flue gas can be carried out step by step to further improve the thermal efficiency;

[0011] As a further improvement of the present utility model, an economizer and an air preheater are arranged in sequence in the tail flue; heat exchange with the flue gas can be carried out step by step to further improve the thermal efficiency;

[0012] In summary, the present utility model can solve the problem of contamination and corrosion of the boiler heating surface, and is applicable to coal types with different alkali metal contents, realizing the stable and efficient operation of burning high-alkali coal purely. Description of the Drawings

[0013] Figure 1 It is a structural schematic diagram of an embodiment of the present utility model. Detailed Embodiment

[0014] The present utility model will be further described below with reference to the drawings.

[0015] As Figure 1As shown in the figure, a high-alkali coal circulating fluidized bed boiler of this embodiment includes a furnace 1, a cyclone separator 2, a flue gas duct at the outlet of the cyclone separator 3, an intermediate flue duct 4, and a tail flue duct 5 that are connected in sequence. The lower end of the cyclone separator 2 is connected to the furnace 1 through a loop seal 6; a platen reheater 7 and a high-temperature platen superheater 8 are arranged in the furnace 1; several nozzles 9 in a group of two are symmetrically arranged on the opposite side walls in the flue gas duct at the outlet of the cyclone separator 3; the intermediate flue duct 4 is divided into a downward flue duct 11 and an upward flue duct 12 by a longitudinal water-cooled partition wall 10 connected to its top. The side walls of the downward flue duct 11 and the upward flue duct 12 are both steam-cooled casings, and steam heat exchange tube bundles 13 are arranged on both steam-cooled casings. Water-cooled heat exchange tube bundles 14 are arranged on both side surfaces of the longitudinal water-cooled partition wall 10; a water-cooled tube bundle 15, an intermediate superheater 16, and a low-temperature superheater 17 are arranged in sequence from bottom to top in the upward flue duct 12; an economizer 18 and an air preheater 19 are arranged in sequence in the tail flue duct 5.

[0016] During use, the high-temperature platen superheater 8 and the platen reheater 7 are arranged in the furnace 1. By using the erosion of a large amount of fluidized circulating materials in the furnace, the corrosion caused by the contamination of alkali metals on the two heating surfaces can be avoided; several nozzles in the flue gas duct at the outlet of the cyclone separator 3 can spray water or low-temperature steam to quickly cool the high-temperature flue gas, providing a basis for the downstream heating surfaces to avoid the contamination-sensitive temperature range; the flue gas flows through the downward flue duct 11 and the upward flue duct 12, passes through the steam heat exchange tube bundles 13 on the inner side thereof and is coupled with the heat exchange tube bundles 14 on both sides of the longitudinal water-cooled partition wall 10 to further cool the flue gas, so that the temperature of the flue gas at the outlet of the downward flue duct 11 is lower than 600 °C. Even when burning coal with a high alkali metal content, the alkali metal compounds in it can be cooled and solidified into a solid state. Coupled with the subsequent further cooling of the water-cooled tube bundle 15, the downstream heating surfaces can avoid the contamination-sensitive temperature range and completely solve the problem of contamination and corrosion of the boiler tail heating surfaces. It can be applicable to coal types with different alkali metal contents and achieve stable and efficient operation of pure combustion of high-alkali coal; the intermediate superheater 16, the low-temperature superheater 17, the economizer 18, and the air preheater 19 can exchange heat with the flue gas step by step to further improve the thermal efficiency;

[0017] The above embodiments are described, but it should be understood that the above embodiments are only for the purpose of exemplification and illustration, and are not intended to limit the present invention to the scope of the described embodiments.

Claims

1. A high-alkali coal circulating fluidized bed boiler, comprising a furnace, a cyclone separator, a cyclone separator outlet flue, an intermediate flue and a tail flue connected in sequence, wherein the lower end of the cyclone separator is connected to the furnace through a return device; characterized in that: A platen reheater and a high-temperature platen superheater are provided in the furnace; several nozzles are provided in the cyclone separator outlet flue; the middle flue is divided into a descending flue and an ascending flue by a longitudinal water-cooled partition wall connected to its top, and water-cooled heat exchange tube bundles are provided on both sides of the longitudinal water-cooled partition wall; a water-cooled tube bundle is provided in the ascending flue.

2. A high-alkali coal circulating fluidized bed boiler as claimed in claim 1, characterized in that: The side walls of the descending flue and the ascending flue are both steam-cooled walls, and the steam-cooled walls are provided with steam heat exchange tube bundles.

3. A high-alkali coal circulating fluidized bed boiler as claimed in claim 1 or 2, characterized in that: The plurality of nozzles are symmetrically arranged in a group of two in the flue gas outlet of the cyclone separator.

4. A high-alkali coal circulating fluidized bed boiler as claimed in claim 3, characterized in that: A medium-temperature superheater and a low-temperature superheater are arranged in sequence in the ascending flue at the rear side of the water-cooled tube bundle.

5. A high-alkali coal circulating fluidized bed boiler as claimed in claim 4, characterized in that: Economizer and air preheater are arranged in the tail flue in sequence.

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