A high-efficiency ammonia direct injection system arranged in the circular flue at the outlet of the gas turbine

Abstract

The present invention discloses a high-efficiency ammonia direct injection ammonia injection system arranged in a circular flue at the outlet of a gas turbine. The ammonia storage tank and the high-pressure gas storage tank are connected to a premixer and then connected to an ammonia injection device. The ammonia injection device is arranged in the circular flue section at the outlet of the gas turbine. The ammonia injection device includes a plurality of ammonia injection branch pipes arranged along the circular flue at the outlet of the gas turbine and in a circular ring structure. Each ammonia injection branch pipe includes a plurality of discontinuous arc segment branch pipes. A nozzle is arranged on each arc segment branch pipe. The ammonia sprayed from the ammonia storage tank and the high-pressure compressed air sprayed from the high-pressure gas storage tank are mixed in the premixer and enter the circular flue at the outlet of the gas turbine through the ammonia injection device. The high-efficiency ammonia direct injection ammonia injection system arranged in the circular flue at the outlet of the gas turbine provided by the present invention has a long distance between the ammonia injection device and the denitration catalyst, and has a sufficient mixing distance. After the ammonia is sprayed in, it evaporates first and then mixes evenly with the flue gas, reducing the workload of ammonia injection leveling in the later stage, overcoming the problem of denitration commissioning under unit startup and low load, and meeting the full-load denitration ammonia supply.

Description

Technical Field

[0001] The invention belongs to the technical field of pollutant emission control, and in particular relates to a high-efficiency ammonia water direct injection ammonia injection system arranged in a circular flue at a gas turbine outlet. Background Art

[0002] At present, the emission control of nitrogen oxides from gas turbine units is becoming increasingly stringent. The emission standards for nitrogen oxides from gas turbines in many places in China require that nitrogen oxides be controlled at 50mg / m 3 Some developed countries even require nitrogen oxides to be controlled within 15-30 mg / m 3 Within.

[0003] NOx emitted by gas turbine units mainly comes from thermal NOx generated at high temperatures. At present, there are two main types of NOx control technologies applicable to gas turbines: controlling the flame temperature of the combustion process, the technologies include water injection method, steam injection method and premixed flame method, controlling the generation of thermal NOx by lowering the flame temperature; for the NOx that has been generated, arranging a catalyst in the waste heat boiler, using amino reductants to react with NOx to control NOx emissions. Most gas turbine units adopt a technical route that combines the two, that is, low nitrogen in the furnace + SCR denitrification outside the furnace.

[0004] At present, there are two main types of reductant preparation in the off-furnace SCR process:

[0005] (1) Urea pyrolysis: Urea is pyrolyzed in an ammonia preparation device outside the engine through heat source introduction to prepare ammonia, which is then sprayed into the flue through an ammonia spray grid for denitrification. The process and equipment are complex, occupying a large area, and it is difficult to introduce heat sources and prepare and store ammonia. The system pipelines are complex and it is difficult to meet the compact layout requirements of the engine. The urea pyrolysis response is too long, and the pyrolysis reactor is prone to problems during long-term operation, which affects the denitrification efficiency of the engine.

[0006] (2) Ammonia evaporation: Ammonia water of a certain concentration is transported to the evaporator inlet through an ammonia supply pump and an ammonia flow control device to supply ammonia water to the ammonia evaporator of the waste heat boiler. In the ammonia evaporation system, compressed air atomizes the ammonia water into tiny particles to ensure that the evaporation time is shortened. The dilution fan blows the hot flue gas extracted from the downstream flue of the SCR reactor into the evaporator to quickly evaporate the ammonia water atomized by compressed air. The evaporated ammonia and flue gas mixture enters the main pipe of the ammonia injection grid system together.

[0007] In addition, most ammonia injection grids are arranged between the hot surface modules of the waste heat boiler, and are short from the catalyst. It is difficult to ensure the uniformity and thoroughness of the mixing of flue gas and ammonia through the ammonia injection grids, and it makes it difficult to optimize and adjust the ammonia injection. Some areas cannot be regulated, and the uniformity of ammonia injection is low. Summary of the invention

[0008] In order to solve the technical problems existing in the prior art, the purpose of the present invention is to provide a high-efficiency ammonia water direct injection ammonia injection system arranged in a circular flue at the outlet of a gas turbine.

[0009] In order to achieve the above purpose and the above technical effect, the technical solution adopted by the present invention is:

[0010] A high-efficiency ammonia direct injection ammonia injection system arranged in a circular flue at a gas turbine outlet, comprising an ammonia water storage tank, a high-pressure gas storage tank, a premixer and an ammonia injection device, wherein the ammonia water storage tank and the high-pressure gas storage tank are respectively connected to the premixer and then connected to the ammonia injection device through the premixer, the ammonia injection device is arranged in the circular flue section at the gas turbine outlet, the ammonia injection device comprises a plurality of ammonia injection branch pipes arranged at intervals along the circular flue at the gas turbine outlet and in a circular ring structure, the ammonia injection branch pipes are connected to the premixer, each ammonia injection branch pipe comprises a plurality of discontinuous arc segment branch pipes, each arc segment branch pipe is provided with a plurality of nozzles, the ammonia water sprayed from the ammonia water storage tank and the high-pressure gas sprayed from the high-pressure gas storage tank are mixed in the premixer and enter the circular flue at the gas turbine outlet through the ammonia injection device, and ammonia gas is sprayed through the nozzles and mixed with the flue gas in the circular flue section at the gas turbine outlet.

[0011] Furthermore, a first flow meter is arranged between the ammonia water storage tank and the premixer.

[0012] Furthermore, the high-pressure gas storage tank is connected to the centrifugal fan, and a second flow meter is arranged between the high-pressure gas storage tank and the premixer.

[0013] Furthermore, the outer diameter of the ammonia injection branch pipe in the circular flue section at the gas turbine outlet decreases along the flue gas flow direction and is arranged forward in sequence. The outer diameter of the ammonia injection branch pipe in the outer circle is larger than the outer diameter of the ammonia injection branch pipe in the inner circle and is arranged in sequence in a cone shape. The distance between two adjacent ammonia injection branch pipes in the flue gas flow direction is 20-30 cm.

[0014] Furthermore, the minimum radius difference between the outer circle branch pipe and the inner circle branch pipe in the ammonia injection branch pipe is 10-20 cm.

[0015] Furthermore, the nozzle and the flue gas flow direction in the circular flue section at the outlet of the combustion engine are at an angle of 100-140 degrees.

[0016] Furthermore, an internal thread structure is provided in the nozzle, and the nozzle diameter is 2-3 cm.

[0017] Furthermore, the thread height of the internal thread structure is 1.2-1.5 cm, and the thread width is 0.3-0.5 cm.

[0018] Furthermore, the nozzles on the outer ammonia injection branch pipe in the circular flue section at the outlet of the gas turbine and which spray inward (in the direction of flue gas flow) have their injection direction aligned with the central axis of the inner ammonia injection branch pipe, so that the injected ammonia / air can form a good mixing disturbance.

[0019] Furthermore, a manual valve is also provided on the arc segment branch pipe for connecting with the main pipe to adjust the ammonia gas spray flow rate.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] The invention discloses a high-efficiency ammonia water direct injection ammonia injection system arranged in a circular flue at a gas turbine outlet. The ammonia injection device is moved forward to the circular flue section at the gas turbine outlet, which is far away from the denitration catalyst and has a sufficient mixing distance. The ammonia water direct injection method is adopted, and the temperature radiation of the high-temperature flue gas is utilized to make the ammonia water evaporate directly into ammonia gas after being sprayed, and then more evenly mixed with the flue gas. There is no need to use an ammonia water evaporator, which reduces investment. There is no need to use an additional heat source (hot air / steam heating heat exchange system), which reduces the later operation cost. The system is simple and the maintenance workload is small. The ammonia injection device is simply arranged, and the ammonia gas prepared by spraying ammonia water is more easily mixed evenly with NOx in the flue gas, which reduces the workload of ammonia injection leveling in the later stage, is conducive to overcoming the denitration commissioning problems of the unit at startup and low load, and meets the full-load denitration ammonia supply. Compared with the existing In the ammonia preparation device based on the transition flue at the outlet of the power plant gas turbine (Chinese patent, publication number CN202246107U) and a dual-fluid spray gun structure suitable for flue-type urea direct injection pyrolysis process (Chinese patent, publication number CN106955593A), urea pyrolysis is used to prepare ammonia. The time required for gasification of ammonia water is short, the residence time in the circular flue is sufficient, the decomposition is thorough, and the utilization rate of the reducing agent is high; the high-pressure gas storage tank is combined with the ammonia spraying device to ensure that the flow rate of the injected ammonia meets the injection stroke requirements; the ammonia spraying branch pipe adopts multi-point distribution, and each nozzle is designed with a unique internal thread structure to allow the mixed gas to be swirled before being sprayed, so that the sprayed ammonia is mixed more evenly. At the same time, manual valves are set on different ammonia spraying branches to make it have regional flow regulation. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a schematic diagram of the overall structure of the present invention;

[0023] Figure 2 It is a front view of the ammonia injection device of the present invention;

[0024] Figure 3 It is a side view of the ammonia injection device of the present invention. DETAILED DESCRIPTION

[0025] The embodiments of the present invention are described in detail below so that the advantages and features of the present invention can be more easily understood by those skilled in the art, thereby making a clearer and more definite definition of the protection scope of the present invention.

[0026] like Figure 1-3As shown, a high-efficiency ammonia water direct injection ammonia injection system arranged in a circular flue at the outlet of a gas turbine, taking the cross-section of the flue at the outlet of the gas turbine as an example, comprises an ammonia water storage tank 1, a high-pressure gas storage tank 2, a premixer 3 and an ammonia injection device 4, the ammonia water storage tank 1 and the high-pressure gas storage tank 2 are respectively connected to the premixer 3 and then connected to the ammonia injection device 4 through the premixer 3, the ammonia injection device 4 is arranged in the circular flue section at the outlet of the gas turbine, the ammonia injection device 4 comprises a plurality of ammonia injection branch pipes 5 arranged at intervals and in a circular ring structure along the circular flue at the outlet of the gas turbine, each ammonia injection branch pipe 5 can be connected to the premixer 3, so as to facilitate the subsequent ammonia injection operation Each ammonia injection branch pipe 5 includes a plurality of discontinuous arc segment branches 6, and a plurality of nozzles 7 are arranged on each arc segment branch pipe 6. Ammonia water of a certain concentration (20%) sprayed from the ammonia water storage tank 1 and high-pressure compressed air sprayed from the high-pressure gas storage tank 2 are mixed in the premixer 3, and then enter the circular flue at the outlet of the combustion engine through the ammonia injection device 4 (ammonia injection branch pipe 5 and arc segment branch pipe 6). Since the flue gas temperature here is relatively high, the high-flow rate ammonia water and air mixture is directly evaporated into a mixed gas of ammonia and high-temperature gas, which is sprayed out through the nozzle 7 and mixed with the flue gas in the circular flue at the outlet of the combustion engine.

[0027] A first flow meter 8 is provided between the ammonia water storage tank 1 and the premixer 3 for detecting the flow rate of the ammonia water.

[0028] The high-pressure gas storage tank 2 is connected to the centrifugal fan 9, and a second flow meter 10 is arranged between the high-pressure gas storage tank 2 and the premixer 3 for detecting the flow rate of the high-pressure compressed air.

[0029] Figure 2-3 Schematic diagram of the structure of the ammonia injection device of the present invention. Since the number, shape, position, etc. of the nozzle 7 are not specifically limited, Figure 2-3 The nozzle 7 in FIG. 1 is not completely drawn. Figure 3 The direction of the middle arrow is from the outer circle to the inner circle. The outer diameter of the ammonia injection branch pipe 5 in the circular flue section at the gas turbine outlet decreases along the flue gas flow direction and is arranged forward in sequence. The outer diameter of the ammonia injection branch pipe 5 in the outer circle is larger than the outer diameter of the ammonia injection branch pipe 5 in the inner circle. They are arranged in sequence in a cone shape. The distance between two adjacent ammonia injection branch pipes 5 in the flue gas flow direction is 20-30cm. The ammonia injection branch pipe 5 located in the inner circle is closer to the denitrification catalyst layer than the ammonia injection branch pipe 5 in the outer circle. The latest difference in radius between the outer circle ammonia injection branch pipe 5 and the inner circle ammonia injection branch pipe 5 is 10-20cm, and it is more than 10m away from the denitrification catalyst layer.

[0030] Each ammonia injection branch pipe 5 can be divided into a plurality of discontinuous arc segment branch pipes 6. A manual valve connected to the ammonia injection branch pipe 5 is arranged on each arc segment branch pipe 6 to adjust the ammonia injection flow rate.

[0031] The cylindrical diameter of the nozzle 7 is 2-3 cm, and an internal thread structure (not shown) is designed inside the nozzle 7, with a thread height of 1.2-1.5 cm and a thread width of 0.3-0.5 cm. Ammonia and air travel in a spiral inside the nozzle 7 before being sprayed, generating good turbulence.

[0032] As a more preferred embodiment, the nozzle 7 can be designed in two rows on the pipe wall of each circular arc branch pipe 6 according to actual needs. The injection direction of the nozzle 7 forms a certain angle with the flue gas flow direction. Preferably, the nozzle 7 is 100-140° to the flue gas flow direction in the circular flue section at the gas turbine outlet. More preferably, the injection direction of the nozzle 7 located on the outer circle ammonia injection branch pipe 5 in the circular flue section at the gas turbine outlet and injecting toward the flue gas flow direction is aligned with the central axis of the inner circle ammonia injection branch pipe 5, so that the injected ammonia / air can form a good mixing disturbance, which cooperates with the internal thread of the nozzle 7 to promote a good mixing disturbance of ammonia, air and flue gas.

[0033] The number, shape, position, etc. of the ammonia injection branch pipe 5, the arc segment branch pipe 6, and the nozzle 7 of the present invention are not specifically limited and are determined according to the unit capacity and the amount of ammonia injection required, and only the stability of the ammonia injection device and the refined ammonia injection requirements need to be ensured.

[0034] The gas turbine outlet flue of the present invention can be designed into other shapes. To fully utilize the cross-sectional space, the structures of all ammonia injection branch pipes 5 in the gas turbine outlet flue section can be adapted to the flue.

[0035] Parts not specifically described in the present invention may adopt existing technologies and will not be described in detail here.

[0036] The above descriptions are merely embodiments of the present invention and are not intended to limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the contents of the present invention specification and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A high-efficiency ammonia water direct injection system arranged at the circular flue at the outlet of the gas turbine, characterized in that: It comprises an ammonia water storage tank, a high-pressure gas storage tank, a premixer and an ammonia spraying device, wherein the ammonia water storage tank and the high-pressure gas storage tank are respectively connected with the premixer and then connected with the ammonia spraying device through the premixer, the ammonia spraying device is arranged at the circular flue section at the gas turbine outlet, the ammonia spraying device comprises a plurality of ammonia spraying branch pipes arranged at intervals along the circular flue section at the gas turbine outlet, each ammonia spraying branch pipe comprises a plurality of discontinuous arc segment branch pipes, each arc segment branch pipe is provided with a plurality of nozzles, the ammonia water sprayed from the ammonia water storage tank and the high-pressure gas sprayed from the high-pressure gas storage tank are mixed in the premixer and enter the circular flue section at the gas turbine outlet through the ammonia spraying device, and ammonia gas is sprayed through the nozzle and mixed with the flue gas in the circular flue section at the gas turbine outlet; The outer diameter of the ammonia injection branch pipe in the circular flue section at the gas turbine outlet decreases along the flue gas flow direction, and is arranged forward in sequence, and the distance between two adjacent ammonia injection branch pipes in the flue gas flow direction is 20-30 cm; The radius difference between the outer ring ammonia injection branch pipe and the inner ring ammonia injection branch pipe in the ammonia injection branch pipe is 10-20 cm; The nozzle is 100-140 degrees away from the flue gas flow direction in the circular flue section at the engine outlet; The nozzles on the outer ammonia injection branch pipe in the circular flue section at the gas turbine outlet and injecting toward the flue gas flow direction have their injection directions aligned with the central axis of the inner ammonia injection branch pipe.

2. According to claim 1, a high-efficiency ammonia water direct injection system arranged in a circular flue at a gas turbine outlet is characterized in that: A first flow meter is arranged between the ammonia water storage tank and the premixer.

3. The high-efficiency ammonia water direct injection system arranged in the circular flue at the outlet of the gas turbine according to claim 1 is characterized in that: The high-pressure gas storage tank is connected to the centrifugal fan, and a second flow meter is arranged between the high-pressure gas storage tank and the premixer.

4. The high-efficiency ammonia water direct injection system arranged in the circular flue at the outlet of the combustion engine according to claim 1 is characterized in that: An internal thread structure is arranged in the nozzle.

5. The high-efficiency ammonia water direct injection system arranged in the circular flue at the outlet of the combustion engine according to claim 4 is characterized in that: The thread height of the internal thread structure is 1.2-1.5 cm, and the thread width is 0.3-0.5 cm.

6. The high-efficiency ammonia water direct injection system arranged in the circular flue at the outlet of the gas turbine according to claim 1 is characterized in that: A manual valve is also arranged on the arc segment branch pipe.

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