Direct spray humidification low nitrogen energy-saving recovery system

Abstract

The present invention discloses a direct spray humidification type low nitrogen energy-saving recovery system, including a gas boiler, a low nitrogen burner, an economizer, a spray type flue gas heat recovery device, a spray type air heating humidifier, a fan, a delivery water pump, a return water pump, and a plate heat exchanger; the gas boiler exhaust port is connected to the inner cavity of the spray type flue gas heat recovery device through the economizer, and the flue gas in the spray type flue gas heat recovery device is cooled by the cooling water sprayed from the first spray pipe, and then discharged to the atmosphere from the chimney on the top of the spray type flue gas heat recovery device; the heated cooling water is sent to the second spray pipe in the spray type air heating humidifier through the first delivery water pump, and the temperature of the gas boiler combustion air entering the spray type air heating humidifier is heated, and the other way is sent to the plate heat exchanger through the second delivery water pump. The present invention solves the problem of reduced output and reduced thermal efficiency of gas boilers caused by FGR technology, and achieves NOx below 30mg / Nm 3 emission standards.

Description

Technical Field

[0001] The invention relates to a gas boiler combustion system, in particular to a direct spraying humidification type low-nitrogen energy-saving recovery system. Background Art

[0002] In order to reduce the nitrogen oxides in the exhaust gas of gas boilers, FGR (flue gas recirculation) technology is currently adopted, that is, by introducing part of the boiler exhaust gas back to the boiler furnace, the flue gas flow rate in the furnace is increased, the nitrogen concentration, oxygen concentration and temperature in the furnace are reduced to inhibit the production of nitrogen oxides; at the same time, a separate indirect heat exchange condensing economizer is adopted to reduce the exhaust gas temperature and achieve heat recovery. Its shortcomings are: 1. The introduction of boiler exhaust gas back to the boiler furnace causes a decrease in the amount of fuel and air entering the furnace, a decrease in heat exchange efficiency, a decrease in boiler steam production and a decrease in thermal efficiency; 2. It causes unstable combustion flames and a high CO content; 3. Condensed water is produced in the backfired flue gas, which will corrode the burner; 4. When the boiler is running at low load, it is impossible to ensure that nitrogen oxides meet the emission standards; 5. The boiler and the heat recovery device are two devices, which are complex to control and occupy a large area. Summary of the invention

[0003] The present invention aims to provide a direct spray humidification type low nitrogen energy-saving recovery system to reduce nitrogen oxides in boiler tail gas emissions and improve the thermal efficiency of gas boilers.

[0004] To achieve the above object, the present invention adopts the following technical solutions:

[0005] The direct spray humidification low-nitrogen energy-saving recovery system of the present invention comprises a gas boiler, a low-nitrogen burner, an economizer, a spray-type flue gas heat recovery device, a spray-type air heating humidifier, a fan, a water delivery pump, a water return pump, and a plate heat exchanger; the gas boiler exhaust port is connected to the inner cavity of the spray-type flue gas heat recovery device through the economizer, and the economizer is used to cool the flue gas and send it into the spray-type flue gas heat recovery device. The flue gas in the spray-type flue gas heat recovery device is cooled by the cooling water sprayed from the first spray pipe and then discharged into the atmosphere from the chimney on the top of the spray-type flue gas heat recovery device; the heated cooling water One route is sent into the second spray pipe in the spray air heating humidifier through the first delivery water pump to heat the temperature of the gas boiler combustion air entering the spray air heating humidifier, and the heated combustion air is sent into the low-nitrogen burner from the air supply pipe and the fan at the top of the spray air heating humidifier, and the cooled cooling water is sent into the first spray pipe for spraying through the return water pump; the other route is sent into the tube side of the plate heat exchanger through the second delivery water pump, and is sent into the first spray pipe for spraying after heat exchange and cooling with the soft water in the shell side of the plate heat exchanger, and the heated soft water is sent to the deaerator or other heat-using end of the gas boiler.

[0006] Furthermore, a smoke exhaust bypass pipe is provided between the economizer outlet and the chimney, and a smoke exhaust electric butterfly valve is provided on the smoke exhaust bypass pipe.

[0007] Furthermore, a combustion air bypass pipe is provided between the combustion air inlet of the spray-type air heating humidifier and the air supply pipe, and a combustion air electric butterfly valve is provided on the combustion air bypass pipe.

[0008] The invention has the advantage of solving the problem of reduced output and reduced thermal efficiency of gas boilers caused by FGR technology. Gas boilers and low-nitrogen burners can achieve NOx below 30mg / Nm without any modification. 3 The overall thermal efficiency of the gas boiler system is improved by 5-8%, making the operation safer and more stable. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 It is a structural schematic diagram of the system of the present invention. DETAILED DESCRIPTION

[0010] The following is a detailed description of an embodiment of the present invention in conjunction with the accompanying drawings. This embodiment is implemented on the premise of the technical solution of the present invention, and a detailed implementation method and a specific operation process are given, but the protection scope of the present invention is not limited to the following embodiment.

[0011] The direct spray humidification low-nitrogen energy-saving recovery system described in the present invention includes a gas boiler 1, a low-nitrogen burner 2, an economizer 3, a spray-type flue gas heat recovery device 4, a spray-type air heating humidifier 5, a fan 6, a first water delivery pump 7.1, a second water delivery pump 7.2, a return water pump 8, and a plate heat exchanger 9.

[0012] The flue gas discharged from the gas boiler 1 is cooled to 120°C by the economizer 3 and sent to the spray type flue gas heat recovery device 4 for heat exchange with the cooling water atomized by the first spray pipe. The flue gas is cooled to 50°C and then discharged into the atmosphere through the chimney 10; the water vapor in the flue gas is condensed to release a large amount of heat which is absorbed by the cooling water, so that the water temperature rises to 50-60°C.

[0013] The cooling water heated to 50-60°C is delivered to the second spray pipe in the spray air heating humidifier 5 through the first water delivery pump 7.1, and after being atomized, it exchanges heat and moisture with the combustion air entering the spray air heating humidifier 5, so that the nitrogen concentration and oxygen concentration in the combustion air decrease; the combustion air temperature increases to about 55°C and the humidity increases to about 95%, and is delivered to the low-nitrogen burner 2 through the air supply duct 13 and the fan 6, and then delivered to the furnace through the low-nitrogen burner 2; this combustion air causes the combustion reaction temperature to decrease in the furnace, and the nitrogen concentration and oxygen concentration also decrease at the same time, thereby resisting the formation of nitrogen oxides and ensuring that the nitrogen oxide value is less than 30mg / Nm 3 .

[0014] The increase in the temperature of the combustion air allows more heat to heat the heat-carrying fluid of the gas boiler 1 after the natural gas is burned; the soft water of the gas boiler 1 is transported by the return pump 8 back to the first spray pipe in the spray type flue gas heat recovery device 4 to exchange heat with the flue gas.

[0015] The cooling water heated to 50-60℃ enters the tube side of the plate heat exchanger 9 through the second water delivery pump 7.2, and exchanges heat with the 20℃ deaerator feed water in the shell side of the plate heat exchanger 9, thereby increasing the temperature of the deaerator feed water (soft water), thereby reducing the use of deaerator steam. Of course, the return water temperature of the heating network can also be heated to reduce the consumption of natural gas.

[0016] A smoke exhaust bypass pipe 11 is provided between the outlet of the economizer 3 and the chimney 10, and a smoke exhaust electric butterfly valve 12 is provided on the smoke exhaust bypass pipe 11. A combustion air bypass pipe 14 is provided between the combustion air inlet of the spray air heating humidifier 5 and the air supply pipe 13, and a combustion air electric butterfly valve 15 is provided on the combustion air bypass pipe 14. By controlling the combustion air electric butterfly valve 15 and the smoke exhaust electric butterfly valve 12, the direct spray humidification type low nitrogen energy-saving recovery system can be bypassed and closed.

Claims

1. A direct spray humidification low nitrogen energy-saving recovery system, characterized by: The invention comprises a gas boiler, a low nitrogen burner, an economizer, a spray type flue gas heat recovery device, a spray type air heating humidifier, a fan, a delivery water pump, a return water pump, and a plate heat exchanger; the exhaust port of the gas boiler is connected with the inner cavity of the spray type flue gas heat recovery device through the economizer; the economizer is used to cool the flue gas and send it into the spray type flue gas heat recovery device; the flue gas in the spray type flue gas heat recovery device is cooled by the cooling water sprayed from the first spray pipe and then discharged into the atmosphere from the chimney at the top of the spray type flue gas heat recovery device; the heated cooling water is sent into the air through the first delivery water pump; In the second spray pipe in the spray air heating humidifier, the temperature of the gas boiler combustion air entering the spray air heating humidifier is heated, and the heated combustion air is sent into the low-nitrogen burner from the air supply duct and the fan at the top of the spray air heating humidifier, and the cooling water after cooling is sent into the first spray pipe through the return water pump; the other way is sent into the plate heat exchanger tube side through the second delivery water pump, and is sent into the first spray pipe after heat exchange and cooling with the soft water in the shell side of the plate heat exchanger, and the heated soft water is sent to the deaerator or other heat-using end of the gas boiler.

2. The direct spray humidification low nitrogen energy-saving recovery system according to claim 1 is characterized in that: A smoke exhaust bypass pipe is arranged between the economizer outlet and the chimney, and a smoke exhaust electric butterfly valve is arranged on the smoke exhaust bypass pipe.

3. The direct spray humidification low nitrogen energy-saving recovery system according to claim 1 or 2, characterized in that: A combustion air bypass pipe is provided between the combustion air inlet of the spray-type air heating humidifier and the air supply pipe, and a combustion air electric butterfly valve is provided on the combustion air bypass pipe.

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