Ammonia combustion circulating fluidized bed boiler system

Abstract

The invention discloses an ammonia combustion circulating fluidized bed boiler system. The system comprises an ammonia storage tank for storing ammonia gas; the upper part of a hearth of the fluidized bed furnace is a dilute-phase region, the lower part of the hearth of the fluidized bed furnace is a dense-phase region, at least one ammonia burner for burning ammonia gas is arranged in the hearth of the fluidized bed furnace, and a nozzle is arranged on the ammonia burner; the air preheater is used for heating air into primary hot air and secondary hot air, and the primary hot air and the secondary hot air enter the dense-phase area through a primary hot air pipeline and a secondary hot air pipeline; the primary fan and the secondary fan are used for supplying air to the air preheater; the cyclone separator is used for collecting combustion products of the ammonia combustor; the tail flue is used for conveying the gas separated by the cyclone separator into the air preheater to perform heat exchange with the primary hot air and the secondary hot air; and the material returning device is used for conveying the solid separated by the cyclone separator to the dense-phase region. High-efficiency and low-pollution combustion of ammonia gas is carried out by adopting a circulating fluidized bed combustion mode, so that zero carbon emission is realized.

Description

Technical Field

[0001] The invention relates to a system for burning ammonia using a circulating fluidized bed boiler, and in particular to a combustion system which adopts a unique countercurrent conveying method to improve the combustion system and reduce nitrogen oxide emissions, and belongs to the technical field of ammonia combustion. Background Art

[0002] With the gradual advancement of my country's "dual carbon" policy, it has become a consensus in the industry to replace traditional fossil fuels with low-carbon or even zero-carbon fuels in the field of traditional thermal power generation. Ammonia, as a clean zero-carbon fuel, has attracted more and more attention from the industry, and related scientific research work has also increased and accelerated year by year. At present, the technical research on ammonia combustion is mostly focused on the combustion of a large proportion of ammonia in traditional pulverized coal boilers, while there is less research on circulating fluidized bed combustion technology for pure ammonia combustion. Summary of the invention

[0003] The technical problem to be solved by the present invention is to provide a circulating fluidized bed combustion system for pure ammonia combustion.

[0004] In order to solve the above problems, the present invention provides an ammonia combustion circulating fluidized bed boiler system, which comprises:

[0005] Ammonia storage tanks for storing ammonia gas;

[0006] A fluidized bed furnace, wherein the upper part of the furnace of the fluidized bed furnace is a dilute phase zone, and the lower part is a dense phase zone. The furnace of the fluidized bed furnace is provided with at least one ammonia burner for burning ammonia gas, and a nozzle is provided on the ammonia burner;

[0007] An air preheater for heating air into primary hot air and secondary hot air, wherein the primary hot air enters the bottom of the dense phase zone through the primary hot air duct, and the secondary hot air enters the side wall of the dense phase zone through the secondary hot air duct;

[0008] Primary and secondary fans for supplying air to the air preheater;

[0009] a cyclone separator for collecting combustion products of an ammonia burner;

[0010] The tail flue is used to transport the gas separated by the cyclone separator to the air preheater for heat exchange with the primary hot air and the secondary hot air;

[0011] A return device used to transport the solids separated by the cyclone separator to the dense phase area.

[0012] Preferably, the ammonia combustion circulating fluidized bed boiler system further comprises a bed material replenishing tank for replenishing material to the dense phase zone.

[0013] Preferably, the ammonia combustion circulating fluidized bed boiler system further comprises a slag cooler for collecting slag in the furnace of the fluidized bed furnace. The slag cooler and the bed material replenishing tank are used to maintain the ash balance for the normal operation of the circulating fluidized bed boiler system.

[0014] Preferably, the ammonia combustion circulating fluidized bed boiler system further comprises a dust collector for removing dust from the flue gas in the tail flue.

[0015] Preferably, the ammonia burner is arranged in the furnace of the fluidized bed furnace in the form of straight tubes, membrane tubes, crossed straight tubes or crossed membrane tube rows.

[0016] More preferably, the tube row of the ammonia burner is coated with fire-resistant and wear-resistant material.

[0017] Preferably, the ammonia burner is provided with at least one layer of nozzles, which are connected to the ammonia delivery pipe, and the ammonia enters the furnace of the fluidized bed furnace through the ammonia delivery pipe and the nozzle. The function of the ammonia burner is: ammonia is introduced from the top of the furnace, enters the dilute phase zone and the dense phase zone through the ammonia burner, and its flow direction is "from top to bottom"; while the air from the air preheater enters the dense phase zone and the dilute phase zone from the bottom of the furnace, and its flow direction is "from bottom to top". Ammonia and air generally show a "countercurrent" flow and meet in the dense phase zone to cause a combustion reaction.

[0018] Preferably, ammonia is introduced into the ammonia burner from the ammonia storage tank, then downwardly enters the furnace of the fluidized bed furnace through the ammonia burner, and enters the dense phase zone through the nozzle of the ammonia burner; the air enters the air preheater for heating through the primary fan and the secondary fan, and the primary hot air enters the dense phase zone through the primary hot air duct, in this area, the primary hot air reacts with the ammonia introduced through the ammonia burner to undergo a combustion reaction; the secondary hot air drawn out from the air preheater enters the dense phase zone through the secondary hot air duct to supplement the air required for combustion and increase combustion efficiency; the flue gas generated after the combustion reaction enters the dilute phase zone, then leaves the fluidized bed furnace and enters the cyclone separator, where gas-solid separation is carried out, the solid particles enter the return device, and return to the dense phase zone through the return device; the flue gas separated from the cyclone separator enters the air preheater through the tail flue to undergo heat exchange with the primary hot air and the secondary hot air.

[0019] Preferably, the air outlet of the primary fan is also connected to the bottom of the fluidized bed furnace through a lower air delivery pipe, and the air outlet of the secondary fan is also connected to the top of the fluidized bed furnace through an upper air delivery pipe; the ammonia burner is also provided with an air delivery pipe, and the lower air delivery pipe and the upper air delivery pipe are connected to the nozzle through the air delivery pipe. A part of the air from the primary fan and the secondary fan is introduced into the ammonia burner through the air pipes, and enters the furnace through the air delivery pipe and the corresponding nozzle of the ammonia burner, as additional supplementary air required for combustion, to assist the combustion of ammonia.

[0020] More preferably, ammonia is introduced into the ammonia burner from the ammonia storage tank, then enters the furnace of the fluidized bed furnace downward through the ammonia burner, and enters the dense phase area through the nozzle of the ammonia burner; air enters the air preheater for heating through the primary fan and the secondary fan, and the primary hot air enters the dense phase area through the primary hot air duct. In this area, the primary hot air reacts with the ammonia introduced through the ammonia burner to generate a combustion reaction; the secondary hot air drawn out from the air preheater enters the dense phase area through the secondary hot air duct to supplement the air required for combustion and increase the combustion efficiency; the air outlets of the primary fan and the secondary fan are respectively The air entering the lower air conveying duct and the upper air conveying duct enters the ammonia burner, and enters the furnace of the fluidized bed furnace through the air conveying pipe and nozzle of the ammonia burner, serving as additional supplementary air required for combustion to assist the combustion of ammonia; the flue gas generated after the combustion reaction enters the dilute phase zone, and then leaves the fluidized bed furnace and enters the cyclone separator, where gas-solid separation is carried out, and the solid particles enter the return material device and return to the dense phase zone through the return material device; the flue gas separated from the cyclone separator enters the air preheater through the tail flue to exchange heat with the primary hot air and the secondary hot air.

[0021] Preferably, the ammonia is replaced by any one of methane, hydrogen, blast furnace gas, or a mixed combustible gas of at least two of them.

[0022] The present invention adopts a circulating fluidized bed combustion method to carry out efficient and low-pollution combustion of ammonia, thereby achieving zero carbon emissions. It is a new technology that meets the needs of future clean energy development. The boiler combustion system proposed in this invention separates the ammonia delivery from the air delivery, and is different from the existing conventional ammonia combustion technology, that is, ammonia is added from the top of the furnace, and enters the dilute phase area and dense phase area of ​​the furnace through the ammonia burner in the furnace, and its flow direction is "from top to bottom"; while the air from the air preheater enters the dense phase area and dilute phase area of ​​the furnace from the bottom of the furnace, and its flow direction is "from bottom to top". Ammonia and air generally show a "countercurrent" flow and meet in the dense phase area of ​​the furnace to undergo a combustion reaction. This not only avoids the mixing of ammonia and air outside the furnace, thereby increasing the safety of ammonia transportation, but also allows for flexible combustion grading inside the furnace and the realization of nitrogen oxide reduction reactions, thereby increasing combustion efficiency and further reducing NO x Emission concentration is a new concept of fluidized bed ammonia combustion technology.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] 1. Ammonia is transported from the top of the furnace into the furnace alone, and its flow direction is "from top to bottom"; while the combustion air enters the furnace from the bottom of the furnace, and its flow direction is "from bottom to top". Ammonia and air generally show a "countercurrent" flow and meet inside the furnace to cause combustion reaction. In this way, ammonia is preheated during the "top-down" transportation process in the furnace, and the distribution of ammonia inside the furnace is more uniform. At the same time, flexible combustion classification can be carried out to ensure high combustion efficiency.

[0025] 2. An ammonia nozzle is set at the furnace outlet area to reduce nitrogen oxides and further reduce the emission concentration of nitrogen oxides;

[0026] 3. Transport ammonia and air separately to eliminate the potential safety hazard of explosion when ammonia mixes with air outside the furnace;

[0027] 4. Directly transporting ammonia and part of the air into the furnace through the ammonia burner in the furnace can make the fuel and air mix more evenly in the furnace, thereby further improving the combustion efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 A schematic diagram of an ammonia combustion circulating fluidized bed boiler system provided in Example 1;

[0029] Figure 2 A schematic diagram of an ammonia combustion circulating fluidized bed boiler system provided in Example 2;

[0030] Figure 3 is a schematic diagram of an ammonia burner in a fluidized bed furnace;

[0031] Figure 4-7 for Figure 3 A cross-sectional view of AA, BB or CC; wherein, Figure 4 Schematic diagram of the arrangement of straight tubes or membrane tubes in Example 1, Figure 5 Schematic diagram of the arrangement of cross straight tubes or cross membrane tube rows in Example 1, Figure 6 Schematic diagram of the arrangement of straight tubes or membrane tubes in Example 2, Figure 7 This is a schematic diagram of the arrangement of the cross straight tubes or cross membrane tube rows in Example 2. DETAILED DESCRIPTION

[0032] In order to make the present invention more clearly understood, preferred embodiments are described in detail below with reference to the accompanying drawings.

[0033] Example 1

[0034] like Figure 1 As shown, an ammonia combustion circulating fluidized bed boiler system provided in this embodiment includes:

[0035] An ammonia storage tank 1 for storing ammonia gas;

[0036] A fluidized bed furnace, wherein the upper part of the furnace of the fluidized bed furnace is a dilute phase zone 4, and the lower part is a dense phase zone 3. The furnace of the fluidized bed furnace is provided with at least one ammonia burner 2 for burning ammonia gas, and the ammonia burner 2 is provided with a nozzle 2-1;

[0037] An air preheater 8 for heating air into primary hot air and secondary hot air, wherein the primary hot air enters the bottom of the dense phase zone 3 through the primary hot air duct 14, and the secondary hot air enters the side wall of the dense phase zone 3 through the secondary hot air duct 15;

[0038] A primary fan 12 and a secondary fan 13 for supplying air to the air preheater 8;

[0039] A cyclone separator 5 for collecting combustion products of the ammonia burner 2;

[0040] A tail flue 7 for conveying the gas separated by the cyclone separator 5 to the air preheater 8 for heat exchange with the primary hot air and the secondary hot air;

[0041] A return device 6 for conveying the solid separated by the cyclone separator 5 to the dense phase zone 3;

[0042] A bed material replenishing tank 11 for replenishing material to the dense phase zone 3;

[0043] A slag cooler 10 for collecting slag in the furnace of the fluidized bed furnace; the slag cooler 10 and the bed material replenishing tank are used to maintain the ash balance for the normal operation of the circulating fluidized bed boiler system;

[0044] A dust collector 9 is used to remove dust from the flue gas in the tail flue 7.

[0045] The ammonia burner 2 is in the furnace of the fluidized bed furnace with straight tubes / membrane tubes ( Figure 4 As shown), cross straight pipe / cross membrane pipe ( Figure 5 The tube row of the ammonia burner 2 is arranged in a row pattern, and fins 2-3 are distributed on the outer surface. The tube row of the ammonia burner 2 is coated with fire-resistant and wear-resistant materials.

[0046] The function of ammonia burner 2 is: ammonia is introduced from the top of the furnace, enters the dilute phase area and the dense phase area through the ammonia burner, and its flow direction is "from top to bottom"; while the air from the air preheater enters the dense phase area and the dilute phase area from the bottom of the furnace, and its flow direction is "from bottom to top". Ammonia and air generally show a "countercurrent" flow and meet in the dense phase area to cause combustion reaction. Figure 3 As shown, the ammonia burner 2 is provided with at least one layer of nozzles 2-1 ( Figure 3In the figure, the AA section, the BB section, and the CC section are respectively located at the bottom, the lower middle, and the upper part of the furnace. The nozzle 2-1 at the AA section is used for burning ammonia; the nozzle 2-1 at the BB section is used to increase the burnout efficiency of ammonia; the nozzle 2-1 at the CC section is used to reduce nitrogen oxides in the combustion products and reduce the emission of nitrogen oxides. The nozzle 2-1 is connected to the ammonia delivery pipe 2-2, and the ammonia enters the furnace of the fluidized bed furnace through the ammonia delivery pipe 2-2 and the nozzle 2-1.

[0047] The working process of the above-mentioned ammonia combustion circulating fluidized bed boiler system is as follows: ammonia is introduced from the ammonia storage tank 1 into the ammonia burner 2, and then downwardly enters the furnace of the fluidized bed furnace through the ammonia burner 2, and enters the dense phase area 3 through the nozzle 2-1 of the ammonia burner 2; air enters the air preheater 8 for heating through the primary fan 12 and the secondary fan 13, and the primary hot air enters the dense phase area 3 through the primary hot air duct 14. In this area, the primary hot air and the ammonia introduced through the ammonia burner 2 undergo a combustion reaction; the secondary hot air drawn out from the air preheater 8 enters the dense phase area 3 through the secondary hot air duct 15 to supplement the air required for combustion and increase the combustion efficiency; the flue gas generated after the combustion reaction enters the dilute phase area 4, and then leaves the fluidized bed furnace and enters the cyclone separator 5, where gas-solid separation is performed, and the solid particles enter the return material device 6 and return to the dense phase area 3 through the return material device 6; the flue gas separated from the cyclone separator 5 enters the air preheater 8 through the tail flue 7 to exchange heat with the primary hot air and the secondary hot air.

[0048] The ammonia is replaced by any one of methane, hydrogen, and blast furnace gas, or a mixed combustible gas of at least two of them.

[0049] Example 2

[0050] like Figure 2 As shown, the difference between this embodiment and embodiment 1 is that:

[0051] The air outlet of the primary fan 12 is also connected to the bottom of the fluidized bed furnace through the lower air delivery pipe 17, and the air outlet of the secondary fan 13 is also connected to the top of the fluidized bed furnace through the upper air delivery pipe 16; the ammonia burner 2 is also connected with an air delivery pipe 2-4, and the lower air delivery pipe 17 and the upper air delivery pipe 16 are connected to the nozzle 2-1 through the air delivery pipe 2-4. The ammonia burner 2 is in the furnace of the fluidized bed furnace with a straight pipe / membrane pipe ( Figure 6 As shown), cross straight pipe / cross membrane pipe ( Figure 7 A portion of the air from the primary fan 12 and the secondary fan 13 is introduced into the ammonia burner 2 through the lower air delivery duct 17 and the upper air delivery duct 16, and enters the furnace through the air delivery pipe 2-4 of the ammonia burner 2 and the corresponding nozzle 2-1, as additional supplementary air required for combustion, to assist the combustion of ammonia.

[0052] The working process of the above-mentioned ammonia combustion circulating fluidized bed boiler system is as follows: ammonia gas is introduced from the ammonia storage tank 1 into the ammonia burner 2, and then enters the furnace of the fluidized bed furnace downward through the ammonia burner 2, and enters the dense phase zone 3 through the nozzle 2-1 of the ammonia burner 2; air enters the air preheater 8 for heating through the primary fan 12 and the secondary fan 13, and the primary hot air enters the dense phase zone 3 through the primary hot air duct 14. In this area, the primary hot air reacts with the ammonia gas introduced through the ammonia burner 2; the secondary hot air drawn out from the air preheater 8 enters the dense phase zone 3 through the secondary hot air duct 15 to supplement the air required for combustion and increase the combustion efficiency; the secondary hot air drawn out from the air preheater 8 enters the dense phase zone 3 through the secondary hot air duct 15 to supplement the air required for combustion and increase the combustion efficiency; The air from the air outlet of the machine 13 enters the lower air conveying duct 17 and the upper air conveying duct 16 respectively, enters the ammonia burner 2, and enters the furnace of the fluidized bed furnace through the air conveying pipe 2-4 and the nozzle 2-1 of the ammonia burner 2, as additional supplementary air required for combustion, to assist the combustion of ammonia; the flue gas generated after the combustion reaction enters the dilute phase zone 4, and then leaves the fluidized bed furnace and enters the cyclone separator 5, where gas-solid separation is carried out, and the solid particles enter the return material device 6 and return to the dense phase zone 3 through the return material device 6; the flue gas separated from the cyclone separator 5 enters the air preheater 8 through the tail flue 7 to exchange heat with the primary hot air and the secondary hot air.

Claims

1. An ammonia combustion circulating fluidized bed boiler system, characterized in that: include: an ammonia storage tank (1) for storing ammonia gas; A fluidized bed furnace, wherein the upper part of the furnace of the fluidized bed furnace is a dilute phase zone (4), and the lower part is a dense phase zone (3), and at least one ammonia burner (2) for burning ammonia gas is arranged in the furnace of the fluidized bed furnace, and a nozzle (2-1) is arranged on the ammonia burner (2); An air preheater (8) for heating air into primary hot air and secondary hot air, wherein the primary hot air enters the bottom of the dense phase zone (3) through a primary hot air duct (14), and the secondary hot air enters the side wall of the dense phase zone (3) through a secondary hot air duct (15); A primary fan (12) and a secondary fan (13) for supplying air to the air preheater (8); a cyclone separator (5) for collecting combustion products of the ammonia burner (2); A tail flue (7) for conveying the gas separated by the cyclone separator (5) to an air preheater (8) for heat exchange with primary hot air and secondary hot air; A return device (6) is used to transport the solid separated by the cyclone separator (5) to the dense phase zone (3).

2. The ammonia combustion circulating fluidized bed boiler system according to claim 1, characterized in that: The invention also comprises a bed material replenishing tank (11) for replenishing material to the dense phase zone (3).

3. The ammonia combustion circulating fluidized bed boiler system according to claim 1, characterized in that: Also included is a slag cooler (10) for collecting slag in the furnace of the fluidized bed furnace.

4. The ammonia combustion circulating fluidized bed boiler system according to claim 1, characterized in that: It also includes a dust collector (9) for removing dust from the flue gas in the tail flue (7).

5. The ammonia combustion circulating fluidized bed boiler system according to claim 1, characterized in that: The ammonia burner (2) is arranged in the furnace of the fluidized bed furnace in the form of straight tubes, membrane tubes, crossed straight tubes or crossed membrane tube rows.

6. The ammonia combustion circulating fluidized bed boiler system according to claim 5, characterized in that: The tube row of the ammonia burner (2) is coated with fire-resistant and wear-resistant material.

7. The ammonia combustion circulating fluidized bed boiler system according to claim 1, characterized in that: The ammonia burner (2) is provided with at least one layer of nozzles (2-1), the nozzles (2-1) are connected to an ammonia gas delivery pipe (2-2), and ammonia gas enters the furnace of the fluidized bed furnace through the ammonia gas delivery pipe (2-2) and the nozzles (2-1).

8. The ammonia combustion circulating fluidized bed boiler system according to any one of claims 1 to 7, characterized in that: The air outlet of the primary fan (12) is also connected to the bottom of the fluidized bed furnace via a lower air delivery pipe (17), and the air outlet of the secondary fan (13) is also connected to the top of the fluidized bed furnace via an upper air delivery pipe (16); the ammonia burner (2) is also provided with an air delivery pipe (2-4), and the lower air delivery pipe (17) and the upper air delivery pipe (16) are connected to the nozzle (2-1) via the air delivery pipe (2-4).

9. The ammonia combustion circulating fluidized bed boiler system according to any one of claims 1 to 7, characterized in that: Ammonia gas is introduced from an ammonia storage tank (1) into an ammonia burner (2), then passes downward through the ammonia burner (2) into the furnace of a fluidized bed furnace, and enters a dense phase zone (3) through a nozzle (2-1) of the ammonia burner (2); air passes through a primary fan (12) and a secondary fan (13) into an air preheater (8) for heating, and primary hot air passes through a primary hot air duct (14) into the dense phase zone (3), in which the primary hot air reacts with the ammonia gas introduced through the ammonia burner (2); the secondary hot air drawn out from the air preheater (8) is passed through a primary hot air duct (14) to the dense phase zone (3); The flue gas passes through the secondary hot air duct (15) and enters the dense phase zone (3) to supplement the air required for combustion and increase the combustion efficiency. The flue gas generated after the combustion reaction enters the dilute phase zone (4) and then leaves the fluidized bed furnace and enters the cyclone separator (5). The gas and solid are separated in the cyclone separator (5). The solid particles enter the return device (6) and return to the dense phase zone (3) through the return device (6). The flue gas separated from the cyclone separator (5) enters the air preheater (8) through the tail flue (7) to exchange heat with the primary hot air and the secondary hot air.

10. The ammonia combustion circulating fluidized bed boiler system according to claim 8, characterized in that: Ammonia gas is introduced from an ammonia storage tank (1) into an ammonia burner (2), then flows downward through the ammonia burner (2) into the furnace of a fluidized bed furnace, and enters a dense phase zone (3) through a nozzle (2-1) of the ammonia burner (2); air enters an air preheater (8) for heating through a primary fan (12) and a secondary fan (13), and the primary hot air enters the dense phase zone (3) through a primary hot air duct (14), in which the primary hot air reacts with the ammonia gas introduced through the ammonia burner (2); the secondary hot air drawn out from the air preheater (8) enters the dense phase zone (3) through a secondary hot air duct (15), supplements the air required for combustion, and increases combustion efficiency; the air outlets of the primary fan (12) and the secondary fan (13) are respectively The air entering the lower air conveying duct (17) and the upper air conveying duct (16) enters the ammonia burner (2), and enters the furnace of the fluidized bed furnace through the air conveying pipe (2-4) and the nozzle (2-1) of the ammonia burner (2), serving as additional supplementary air required for combustion, thereby assisting the combustion of ammonia; the flue gas generated after the combustion reaction enters the dilute phase zone (4), then leaves the fluidized bed furnace and enters the cyclone separator (5), where gas-solid separation is performed, and solid particles enter the return material device (6), and are returned to the dense phase zone (3) through the return material device (6); the flue gas separated from the cyclone separator (5) enters the air preheater (8) through the tail flue (7), and performs heat exchange with the primary hot air and the secondary hot air.

11. The ammonia combustion circulating fluidized bed boiler system according to claim 1, characterized in that: The ammonia is replaced by any one of methane, hydrogen, and blast furnace gas, or a mixed combustible gas of at least two of them.

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