CN209540885U - A kind of warm and humid coupling gas fired-boiler low nitrogen burning system - Google Patents

Abstract

The utility model discloses a low-nitrogen combustion system for a temperature-humidity coupling gas boiler, which comprises a burner, a furnace, a phase-change condensation water collector, a mixer, a temperature-humidity regulator and the like. The phase change condensation water collector is equipped with heat exchange tubes, spray cooling pipe rows and labyrinth water collectors. The inside of the temperature and humidity regulator is equipped with an equalizing orifice plate, a spray humidification tube row and a heat exchange tube. The burner, the furnace, the convection heating surface and the phase change condensation water eliminator are connected in sequence. One inlet of the mixer is connected to the phase change condensation water collector through the recirculation fan, and the mixed air is sent to the burner to participate in the combustion in the furnace. The condensed water of the phase change condensation water collector is collected through the high-level water storage tank, and all of it is sprayed into the temperature and humidity regulator for heating and humidifying the air. The condensed water recovered by the mixer and the temperature and humidity regulator is used to cool the smoke temperature. Thereby reducing the oxygen partial pressure in the combustion air and the flue gas temperature in the furnace. The utility model has the advantages of low water consumption of the system, sensitive adjustment of the humidity of the inlet air, and remarkable effect of reducing gas NO _X emission.

Description

A low-nitrogen combustion system for a temperature-humidity coupled gas-fired boiler

technical field

The utility model relates to a low-nitrogen combustion system of a temperature-humidity coupled gas boiler, which belongs to the technical field of cogeneration of heat and electricity.

Background technique

Energy structure adjustment is an important means of air pollution control. In the future, with the increase of the proportion of clean energy, the consumption of natural gas will increase rapidly. The main air pollutant emitted by natural gas combustion is NO _x . Therefore, the low-nitrogen combustion technology of natural gas is an important technical guarantee for large-scale clean utilization of natural gas in China. As a clean fuel, natural gas is widely used in industrial production and residential heating. As China's environmental protection requirements become increasingly stringent, the limits on nitrogen oxide emissions from gas-fired boilers are also getting higher and higher. Some key areas require new gas-fired boilers to emit less than 30mg/Nm ³ of nitrogen oxides, which brings new challenges to low-nitrogen combustion technology. great challenge.

Therefore, the research and development of low-nitrogen combustion technology with lower emission levels is not only conducive to the stable emission of existing gas-fired boilers, but also can further reduce NO _X emissions, which provides a guarantee for the further reduction of PM2.5 concentration.

The main component of natural gas is methane, the content is generally 95-97% or even higher, and it basically does not contain fuel nitrogen. In the combustion process, it is mainly thermal and rapid NOx. Thermal NOx is the NOx produced by the oxidation of _N2 in the air by _O2 at high temperature, accounting for about 90-95% of the total NOx generation, and is an important generation method for the control of NOx in natural gas combustion.

The method of diluting the flame to reduce the flue gas temperature is a widely used low-nitrogen combustion technology, such as flue gas recirculation and air humidification technology. The addition of recirculated flue gas reduces the oxygen partial pressure of the combustion-supporting air, thereby reducing the combustion rate, the flame temperature in the furnace is also reduced, and the generation of thermal NOx is effectively controlled. However, as the amount of circulating flue gas increases, the oxygen in the air is continuously diluted. At the same time, due to the increase of air flow, the flow field of the burner changes, which may easily cause the instability of flame combustion, or cause the flame to be too long. Affect the normal operation and safety of the boiler. Therefore, how to solve the problems of combustion stability, condensate precipitation and boiler efficiency when the flue gas recirculation rate is further increased is the key to further reducing _NOx emissions from the combustion of natural gas and other gaseous fuels.

Humidifying the air or injecting water into the flame zone to reduce the temperature of the combustion zone can inhibit the formation of thermal NOx. However, the application of humidification technology is limited due to the difficulty of water source and recovery. For example, in the patent document CN108613173A, the gas-gas heat exchange between air and flue gas is used as the heat source for air heating. At the same time, boiler return water is sprayed into the heat exchanger inlet, and recirculated flue gas is added to the heat exchanger outlet. In the patent document CN106500120A, the gas-gas heat exchange is also used to heat the air, and the condensed water is used to humidify the air. However, in the above-mentioned scheme, the gas-gas heat exchange requires a large temperature end difference, which leads to the heat recovery and condensation of the waste heat of the flue gas. The small amount of water, the inability to greatly increase the humidity in the air, and the large size of the heat exchanger all limit the application of this technical solution, and at the same time cannot take into account the contradiction between ultra-low nitrogen and combustion stability.

Utility model content

The utility model aims to provide a low-nitrogen combustion system for a temperature-humidity coupling gas boiler. It can stabilize the combustion flame, greatly reduce the formation of nitrogen oxides, and deeply recover the waste heat and moisture in the flue gas through the phase change condensation water eliminator, effectively saving water and improving boiler efficiency.

The utility model is realized through the following technical solutions:

A low-nitrogen combustion system for a temperature-humidity coupled gas-fired boiler, including a gas-fired boiler, a phase-change condensation water collector, a temperature-humidity regulator, a mixer, and a blower; the gas-fired boiler includes successively connected furnaces and convective heating surfaces; the furnace The internal front end is provided with a burner; the phase change condensation water eliminator is arranged between the convection heating surface and the temperature and humidity regulator, and the phase change condensation water eliminator and the convection heating surface are respectively arranged The flue gas pipeline is connected to the heat exchange working medium pipeline; the phase change condensation water collector forms a circulation connection with the temperature and humidity regulator; the temperature and humidity regulator is connected to the mixer; the The mixer is connected to the flue gas pipeline between the phase change condensation water eliminator and the convection heating surface through a flue gas recirculation fan, and the mixer is connected to the burner; the temperature and humidity regulator 1. A heat exchange working medium pipeline is provided between the phase change condensation water collector and the convective heating surface; the air blower is connected between the mixer and the burner or between the mixer and the temperature and humidity regulator.

In the above technical solution, a high-level water storage tank and a high-level water pump are arranged between the phase-change coagulation water eliminator and the temperature-humidity regulator, and the circuit between the temperature-humidity regulator and the phase-change coagulation water eliminator A low-level water storage tank and a low-level water pump are arranged on the top.

In the above technical solution, the mixer includes an air inlet pipe, an air outlet pipe, a mixing chamber arranged between the air inlet pipe and the air outlet pipe, and a recirculation flue gas inlet pipe and a condensation water pipe arranged on the mixing chamber; the condensation water pipe is provided It is at the bottom of the mixing chamber, and the condensation water pipe is connected with the low water storage tank.

In the above technical solution, the inlet pipe, the outlet pipe and the mixing chamber are coaxially arranged in a cylindrical shape, and the diameter of the mixing chamber is 1.2 to 1.5 times the diameter of the inlet pipe; The mixing chambers are connected with expanding pipes; the recirculation flue gas inlet pipe is circumferentially incised from the side of the mixing chambers.

In the above technical solution, an annular flue is provided outside the mixing chamber, and a number of smoke nozzles are evenly distributed on the annular flue, and the flue gas nozzles are connected to the annular flue and the mixing chamber.

In the above technical solution, the flue gas nozzle is set according to the design flow velocity of 50-60m/s.

In the above technical solution, the phase-change condensation water collector is provided with a phase-change heat pipe, a spray cooling pipe row and a labyrinth water collector in sequence; the spray cooling pipe row is provided with a number of spray cooling pipes, and the spray cooling pipe row The shower cooling pipe is arranged obliquely, and the spray cooling pipe is provided with a number of spray ports facing the side of the phase-change heat pipe, and the spray direction of the spray port is facing the side of the phase-change heat pipe, and the slope is 0-30° upward. °; The labyrinth water eliminator is arranged at the outlet of the phase change coagulation water eliminator, including several V-shaped or I-shaped baffles arranged side by side.

In the above technical solution, the inlet of the temperature and humidity regulator is in the gradual expansion section, and several flow equalization orifice plates are arranged in the gradual expansion section; the spray humidification pipe row and fins are also arranged in the temperature and humidity regulator. Finned heat exchange tubes; the finned heat exchange tubes are arranged close to the outlet section of the temperature and humidity regulator, and the rows of spray humidification tubes are arranged obliquely toward the inlet of the temperature and humidity regulator.

The utility model has the following advantages and beneficial effects: 1) the air is heated through the temperature and humidity regulator, which can prevent the cold air from directly mixing with the recirculation flue gas to produce condensed water; 2) the addition of the recirculation flue gas reduces the The oxygen content of the combustion air is reduced to 18-20%. While reducing the flame combustion rate, the flame temperature in the furnace is effectively cooled, and finally the generation of thermal NOx is reduced; 3) The purpose of spraying and humidification is to ensure the oxygen content of the combustion air Under certain circumstances, increasing the content of triatomic gas in the combustion-supporting air will increase the specific heat capacity of the gas and further reduce the temperature of the combustion flame; 4) The temperature and humidity regulator and the phase change condensation water collector all exchange heat indirectly and directly through gas-liquid, and the heat exchange efficiency High, compact structure of the heat exchanger; 5) The water used for spraying comes directly from the flue gas condensed water, saving water, and at the same time recovering the moisture in the flue gas, which can eliminate the white smoke in the chimney; 6) By increasing the humidity in the air, Reduce the partial pressure of oxygen in the air, and under the combined effect of the two, while realizing ultra-low nitrogen combustion (NOx emission lower than 15mg/Nm ³ (@3.5%)), it can increase the stability of the combustion flame.

Description of drawings

Fig. 1 is a schematic diagram of a low-nitrogen combustion system of a temperature-humidity coupled gas-fired boiler according to an arrangement of the present invention.

Fig. 2 is a schematic diagram of a low-nitrogen combustion system of a temperature-humidity coupled gas-fired boiler according to another arrangement of the present invention.

Fig. 3 is a schematic structural diagram of the phase change coagulation water eliminator involved in the present invention.

Fig. 4 is a schematic structural diagram of the temperature and humidity regulator involved in the present invention.

Fig. 5 is a structural schematic diagram of a mixer in one embodiment of the present invention.

Fig. 6 is a schematic structural view of a mixer according to another embodiment of the present invention: a) a schematic cross-sectional view; b) a schematic structural view.

In the figure: 1—air inlet regulating valve; 2—furnace; 3—convection heating surface; 4—phase change condensation water eliminator; 41—phase change heat pipe; 42—spray cooling pipe row; 43—labyrinth water eliminator ;44—condensate water inlet; 5—flue gas recirculation control valve; 6—flue gas recirculation fan; 7—temperature and humidity regulator; 71—fin heat exchange tube; 72—spray humidification pipe row; – equalizing orifice; 74 – water inlet; 8 – air blower; 9 – mixer; 91 – intake pipe; 92 – diffuser; 93 – recirculation flue gas inlet pipe; Pipe; 96-flue gas nozzle; 97-mixing chamber; 98-outlet pipe; 10-high water storage tank; 11-high water pump; 12-low water storage tank; 13-low water pump; 14-regulating valve.

Detailed ways

Below in conjunction with accompanying drawing, the specific embodiment of the utility model and working process are further described.

The orientation terms such as up, down, left, right, front and rear in this application document are established based on the positional relationship shown in the drawings. If the drawings are different, the corresponding positional relationship may also change accordingly, so this should not be understood as limiting the scope of protection.

As shown in Figures 1 and 2, a temperature-humidity coupled gas-fired boiler low-nitrogen combustion system includes a gas-fired boiler, a phase change condensation water collector 4, a temperature and humidity regulator 7, a mixer 9 and a blower 8. The gas boiler includes a furnace 2 and a convection heating surface 3 connected in sequence. The inner front end of the furnace 2 is provided with a burner. The phase change condensation water eliminator 4 is arranged between the convection heating surface 3 and the temperature and humidity regulator 7 . The phase-change condensation water eliminator 4 and the convective heating surface 3 are respectively provided with flue gas pipelines and heat-exchange working medium pipelines connected to each other. A cyclic connection is formed between the phase change coagulation water collector 4 and the temperature and humidity regulator 7 . The temperature and humidity regulator 7 is also connected to the mixer 9 . The flue gas pipeline between the mixer 9 and the phase change condensation water eliminator 4 and the convective heating surface 3 is connected through a flue gas recirculation fan 6, and a flue gas recirculation fan 6 is arranged between the flue gas recirculation fan 6 and the flue gas pipeline. Circulation control valve 5. The mixer 9 is connected to the burner. The temperature-humidity regulator 7, the phase-change condensation water collector 4 and the convective heating surface 3 are connected by a heat-exchange working medium pipeline. The blower is connected between the mixer and the burner (Figure 1) or between the mixer and the thermohumidifier (Figure 2). An air intake regulating valve 1 is also provided before the burner inlet to adjust the total air volume.

A high-level water storage tank 10 and a high-level water pump 11 are arranged between the phase-change coagulation water collector 4 and the temperature-humidity regulator 7, and a low-level water storage tank 12 is arranged on the circuit between the temperature-humidity regulator 7 and the phase-change cohesion water collector 4 And low level water pump 13.

As shown in FIG. 4 , the phase-change coagulation water eliminator 4 is provided with phase-change heat pipes 41 , spray cooling pipe rows 42 and labyrinth water eliminators 43 in sequence according to the air flow direction. The spray cooling tube row 42 is provided with a number of spray cooling tubes, the spray cooling tubes are arranged obliquely, and the spray cooling tubes are provided with a number of spray ports facing the phase-changing heat pipe 41, and the spraying direction of the spray ports is facing the phase-changing heat pipe 41- sideways and inclined upward at 0-30°. The labyrinth water eliminator 43 is arranged at the outlet of the phase change coagulation water eliminator 4, and includes several V-shaped or I-shaped baffles arranged side by side.

As shown in FIG. 5 , the inlet of the temperature-humidity regulator 7 is in the gradual expansion section, and a number of equalizing orifice plates 73 are arranged in the gradual expansion section, so that the air is evenly distributed and enters the temperature-humidity regulator 7 . The temperature and humidity regulator 7 is also provided with spray humidification tube rows 72 and finned heat exchange tubes 71 . The finned heat exchange tube 71 is arranged near the outlet section of the temperature and humidity regulator 7 . The row of spraying and humidifying pipes 72 is obliquely arranged towards the inlet of the temperature and humidity regulator 7 . The spray humidification pipe row 72 includes a number of spray humidification pipes, on which a number of nozzles facing the incoming air direction are arranged, and the condensed water is sprayed obliquely to the air flow.

The mixer 9 includes an inlet pipe 91 , an outlet pipe 98 , a mixing chamber 97 arranged between the inlet pipe 91 and the outlet pipe 98 , and a recirculation flue gas inlet pipe 93 and a condensed water pipe 94 arranged on the mixing chamber 97 . The condensation water pipe 94 is arranged at the bottom of the mixing chamber 97 , and the condensation water pipe 94 is connected with the low water storage tank 12 .

One of the technical solutions is shown in Figure 5, the inlet pipe 91, the outlet pipe 98 and the mixing chamber 97 are coaxially arranged in a cylindrical shape, and the diameter of the mixing chamber 97 is 1.2 to 1.5 of the diameter of the inlet pipe 91. times; the inlet pipe 91 and the mixing chamber 97 are connected by a diverging pipe 92;

Another technical solution is shown in FIG. 6 . An annular flue 95 is arranged outside the mixing chamber 97. At this time, the cross section of the inlet pipe 91/outlet pipe 98 and the mixing chamber 97 can be circular or rectangular, and the corresponding annular flue 95 is also a circular or rectangular circle. The rectangular section is shown in Figure 6a). A number of flue gas nozzles 96 are evenly distributed on the annular flue 95 , and the flue gas nozzles 96 are connected to the annular flue 95 and the mixing chamber 97 . Figure 6b) shows a mixer with a rectangular cross-section. The flue gas nozzle 96 is set according to the design velocity of 50-60m/s.

The air is evenly distributed through the flow equalizing orifice 73 and then enters the temperature and humidity regulator 7; the spray condensed water is sprayed into the temperature and humidity regulator 7 through the spray humidification pipe row 72. Make the spray condensed water directly contact with the air to exchange heat, while heating the air, part of the condensed water evaporates directly, and the other part of the condensed water droplets are carried by the air to continue heat exchange in the finned heat exchange tube 71 of the temperature and humidity regulator 7 Make the boiler return water enter the finned heat exchange tube 71 of the temperature and humidity regulator 7 to exchange heat with the air carrying the condensed water droplets, so that the condensed water droplets in the air evaporate after absorbing the heat of the boiler return water, and the air absorbs the heat at the same time After that, the temperature rises, and the water vapor saturation partial pressure in the air increases. The amount of boiler return water entering the temperature and humidity regulator 7 is adjusted through the regulating valve 14, and the air at the outlet of the temperature and humidity regulator 7 can be adjusted to 30-50°C.

The humidified and heated air enters the mixer 9 and is evenly mixed with the recirculated flue gas, so that the temperature of the mixed air rises to 50-60° C. and the oxygen partial pressure decreases to 18-20%.

The mixed air is sent into the burner through the air inlet regulating valve 1, so that the natural gas entering the burner is burned to generate high-temperature flue gas; the high-temperature flue gas passes through the heat exchange of the furnace 2 and the convective heating surface 3, and the temperature of the flue gas is reduced to 110-130 ℃.

A part of the flue gas is used as the recirculation flue gas, and under the regulation of the flue gas recirculation regulating valve 5, it enters the mixer 9 through the flue gas recirculation fan 6 and mixes with air to form mixed air. At this time, adjust the amount of recirculated flue gas to be 5-10% of the total flue gas.

Another part of the flue gas enters the phase-change condensation water eliminator 4, and successively passes through the phase-change heat pipe 41 and the spray cooling pipe row 42 for heat exchange, so that the temperature of the flue gas is reduced to 50-60°C. The liquid droplets are collected by the labyrinth water collector 43 under the flue gas. At the same time, the spray waste water and the condensed water in the flue gas all flow into the sump 44, and then flow into the high-level water storage tank 10. After being pressurized by the high-level water pump 11, they are sent into the The spray humidification pipe row 72 of the temperature and humidity regulator 7 is used as spray condensed water to heat and humidify the air. The spray condensed water heats and humidifies the air and then cools down to become condensed water, which flows to the lower water storage tank 12 . At the same time, the condensed water in the mixer 9 is transported from the condensed water pipe 94 to the lower water storage tank 12 for collection. After being pressurized by the low-level water pump 13, the condensed water is sent to the phase change condensation water eliminator 4 to spray and cool down the pipe row 42 to spray and cool the flue gas.

The air is heated through the temperature and humidity regulator 7, which can prevent the cold air from directly mixing with the recirculated flue gas to generate condensed water. The addition of recirculated flue gas reduces the oxygen content of the combustion-supporting air at the burner inlet to 18-19%. While reducing the flame combustion rate, it effectively cools the flame temperature in the furnace, and finally reduces the generation of thermal NOx. The purpose of spray humidification is to increase the triatomic gas content in the combustion air while ensuring the oxygen content of the combustion air, increase the specific heat capacity of the gas, and further reduce the combustion flame temperature. By increasing the humidity in the air and reducing the partial pressure of oxygen in the air, under the combined action of the two, while achieving ultra-low nitrogen combustion (NOx emissions below 15mg/Nm ³ (@3.5%)), the combustion flame can be increased stability.

Boiler return water can be transported to the finned heat exchange tube 71 of the temperature and humidity regulator 7, the phase change heat pipe 41 of the phase change heat pipe 4 and the convective heating surface 3 through the heat exchange working medium pipeline, and then used by users after heat exchange in sequence. A regulating valve is set on the heat exchange working medium pipeline to regulate and distribute the flow.

The above descriptions are only preferred embodiments of the present utility model, and are not intended to limit the present utility model. For those skilled in the art, the present utility model can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present utility model shall be included in the protection scope of the present utility model.

Claims (8)

1. a kind of warm and humid coupling gas fired-boiler low nitrogen burning system, which is characterized in that the low nitrogen burning system includes gas-fired boiler Furnace, phase transformation cohesion water collection device (4), temperature and humidity regulator (7) and mixer (9)；The gas fired-boiler includes the burner hearth being sequentially connected (2) and convection heating surface (3)；Burner hearth (2) interior forward end is provided with burner；Phase transformation cohesion water collection device (4) setting Between the convection heating surface (3) and the temperature and humidity regulator (7), phase transformation cohesion water collection device (4) and the convection current by Cigarette air pipe line is respectively equipped between hot face (3) to be connected with heat-exchange working medium pipeline；Phase transformation cohesion water collection device (4) with it is described warm and humid It is formed and is connected by circulation between adjuster (7)；The temperature and humidity regulator (7) is connected with the mixer (9)；The mixer (9) Cigarette air pipe line between phase transformation cohesion water collection device (4) and the convection heating surface (3) passes through gas recirculating fan (6) It is connected, and the mixer (9) is connected with the burner；The temperature and humidity regulator (7), phase transformation cohesion are water collection device (4) and right It flows and is connected between heating surface (3) equipped with heat-exchange working medium pipeline.

2. the warm and humid coupling gas fired-boiler low nitrogen burning system of one kind according to claim 1, which is characterized in that the phase transformation High-level water storage case (10) and high-order water pump (11), the temperature are provided between cohesion water collection device (4) and the temperature and humidity regulator (7) Circuit between wet adjuster (7) and phase transformation cohesion water collection device (4) is equipped with low level water tank (12) and low level water pump (13)。

3. the warm and humid coupling gas fired-boiler low nitrogen burning system of one kind according to claim 2, which is characterized in that the mixing Device (9) includes air inlet pipe (91), escape pipe (98) and the mixing chamber (97) being arranged between air inlet pipe (91) and escape pipe (98) And the flue gas recycled inlet tube (93) and condensate pipe (94) being arranged on mixing chamber (97)；The condensate pipe (94) sets It sets in mixing chamber (97) bottom, and the condensate pipe (94) is connect with the low level water tank (12).

4. the warm and humid coupling gas fired-boiler low nitrogen burning system of one kind according to claim 3, which is characterized in that the air inlet The cylinder that pipe (91), escape pipe (98) are arranged coaxially with the mixing chamber (97), and the mixing chamber (97) diameter is institute 1.2~1.5 times for stating air inlet pipe (91) diameter；Diffuser (92) are equipped between the air inlet pipe (91) and the mixing chamber (97) Connection；The flue gas recycled inlet tube (93) is cut from the side circumferential direction of mixing chamber (97).

5. the warm and humid coupling gas fired-boiler low nitrogen burning system of one kind according to claim 3, which is characterized in that the mixing Chamber (97) is externally provided with ring-shaped flue (95), ring-shaped flue (95) if on be evenly distributed with dry flue gas spout (96), flue gas spray Mouth (96) connects described ring-shaped flue (95) and the mixing chamber (97).

6. the warm and humid coupling gas fired-boiler low nitrogen burning system of one kind according to claim 5, which is characterized in that the flue gas Spout (96) is arranged by 50~60m/s of design current velocity.

7. the warm and humid coupling gas fired-boiler low nitrogen burning system of one kind according to claim 1, which is characterized in that the phase transformation Phase inversion heat pipe (41), spraying cooling pipe row (42) and labyrinth type water collection device (43) are successively arranged in cohesion water collection device (4)；It is described Spraying cooling pipe arranges (42) and several spraying cooling pipes is arranged, and the spraying cooling pipe is in tilted layout, and spraying cooling pipe court Phase inversion heat pipe (41) side is provided with several spray ports, the spray port injection direction is towards the phase inversion heat pipe (41) it side and tilts upward in 0~30 °；Labyrinth type water collection device (43) setting goes out in phase transformation cohesion water collection device (4) Mouthful, including several V-types being set side by side or I-shaped baffle plate.

8. the warm and humid coupling gas fired-boiler low nitrogen burning system of one kind according to claim 1, which is characterized in that described warm and humid Adjuster (7) entrance is to be equipped with several uniform flow orifices (73) in the divergent segment in divergent segment；In the temperature and humidity regulator (7) It is additionally provided with spray humidification pipe row (72) and fin heat exchange tube (71)；The fin heat exchange tube (71) goes out close to temperature and humidity regulator (7) Mouth section setting, the spray humidification pipe row (72) are in tilted layout towards the temperature and humidity regulator (7) entrance.