A flue gas waste heat utilization and water intake system for a coal-fired boiler co-firing ammonia

Abstract

The invention discloses a flue gas waste heat utilization and water intake system for a coal-fired boiler with ammonia co-firing. The flue gas outlet of the coal-fired boiler is communicated with the flue gas inlet of a low-temperature ammonia preheater. The flue gas outlet of the low-temperature ammonia preheater is communicated with the flue gas inlet of a flue gas condensation water intake device. The flue gas outlet of the flue gas condensation water intake device is communicated with the inlet of a chimney. The liquid ammonia outlet of a liquid ammonia storage tank is communicated with the liquid ammonia inlet of a liquid ammonia vaporizer. The ammonia outlet of the liquid ammonia vaporizer is communicated with the ammonia inlet of the low-temperature ammonia preheater. The ammonia outlet of the low-temperature ammonia preheater is communicated with an ammonia burner on the coal-fired boiler. The cooling water inlet of the liquid ammonia vaporizer is communicated with the cooling water outlet of the flue gas condensation water intake device. The cooling water outlet of the liquid ammonia vaporizer is communicated with the cooling water inlet of the flue gas condensation water intake device. This system can effectively utilize cooling water while vaporizing liquid ammonia and preheat ammonia to prevent secondary condensation.

Description

Technical Field

[0001] The present invention belongs to the technical field of flue gas waste heat recovery, and relates to a flue gas waste heat utilization and water intake system for a coal-fired boiler with ammonia co-firing. Background Art

[0002] As a carbon-free carrier, ammonia has a high hydrogen content and a high volumetric energy density compared to hydrogen, is extremely easy to liquefy, is convenient for transportation and storage, and can be obtained from fossil fuels, biomass, or other renewable resources. The products during the combustion process of ammonia are mainly nitrogen, water, and nitrogen oxides, without the generation of carbon dioxide, sulfur dioxide, and soot, and the flue gas treatment measures are simple. Using ammonia as a substitute for fossil fuels and entering the existing coal-fired boilers for co-firing can effectively reduce the carbon dioxide emissions of coal-fired boilers. When ammonia is co-fired in a coal-fired boiler, water is generally used to vaporize liquid ammonia. Since ammonia is relatively easy to condensate secondary, before the ammonia is sent into the coal-fired boiler for combustion, the ammonia needs to be preheated. Therefore, a coal-fired unit with ammonia co-firing requires a system that can effectively utilize cooling water while vaporizing liquid ammonia and preheat ammonia to prevent secondary condensation. Summary of the Invention

[0003] The purpose of the present invention is to overcome the above-mentioned drawbacks of the prior art, and provides a flue gas waste heat utilization and water intake system for a coal-fired boiler with ammonia co-firing, which can effectively utilize cooling water while vaporizing liquid ammonia and preheat ammonia to prevent secondary condensation.

[0004] To achieve the above purpose, the flue gas waste heat utilization and water intake system for a coal-fired boiler with ammonia co-firing described in the present invention includes a coal-fired boiler, an ammonia burner, a low-temperature ammonia preheater, a dust collector, a desulfurization absorption tower, a flue gas condensation water intake device, a water collecting tank, a condensate water tank, a chimney, a liquid ammonia storage tank, a liquid ammonia vaporizer, and an electric control valve;

[0005] The flue gas outlet of the coal-fired boiler is connected to the flue gas inlet of the low-temperature ammonia preheater, the flue gas outlet of the low-temperature ammonia preheater is connected to the flue gas inlet of the flue gas condensation water intake device through the dust collector and the desulfurization absorption tower, and the flue gas outlet of the flue gas condensation water intake device is connected to the inlet of the chimney;

[0006] The liquid ammonia outlet of the liquid ammonia storage tank is connected to the liquid ammonia inlet of the liquid ammonia vaporizer, the ammonia outlet of the liquid ammonia vaporizer is connected to the ammonia inlet of the low-temperature ammonia preheater, and the ammonia outlet of the low-temperature ammonia preheater is connected to the ammonia burner on the coal-fired boiler;

[0007] The cooling water inlet of the liquid ammonia vaporizer is connected to the cooling water outlet of the flue gas condensation water intake device, and the cooling water outlet of the liquid ammonia vaporizer is connected to the cooling water inlet of the flue gas condensation water intake device;

[0008] A hot water recirculation bypass is provided between the cooling water inlet and the cooling water outlet of the liquid ammonia vaporizer, and an electric control valve is provided on the hot water recirculation bypass.

[0009] A water collecting tank is provided at the bottom of the flue gas condensation water intake device, and the condensation water outlet of the water collecting tank is communicated with the condensation water inlet of the condensation water tank.

[0010] The low-temperature ammonia preheater is a tubular gas-gas heat exchanger, and the heat exchange tubes in the low-temperature ammonia preheater are smooth tubes.

[0011] The heat exchange tubes in the flue gas condensation water intake device are made of titanium tubes.

[0012] The liquid ammonia vaporizer adopts a shell-and-tube heat exchanger, and the heat exchange tubes in the liquid ammonia vaporizer are smooth tubes.

[0013] The flue gas outlet of the low-temperature ammonia preheater is communicated with the flue gas inlet of the flue gas condensation water intake device through a dust collector, an induced draft fan and a desulfurization absorption tower.

[0014] The liquid ammonia outlet of the liquid ammonia storage tank is communicated with the liquid ammonia inlet of the liquid ammonia vaporizer through a liquid ammonia transfer pump.

[0015] The cooling water outlet of the liquid ammonia vaporizer is communicated with the cooling water inlet of the flue gas condensation water intake device through a cooling water circulation pump.

[0016] The present invention has the following beneficial effects:

[0017] When the coal-fired boiler flue gas waste heat utilization and water intake system with ammonia co-firing of the present invention is in specific operation, taking cooling water as the heat source, indirectly exchanging heat through a liquid ammonia vaporizer to evaporate liquid ammonia into ammonia gas, using a tubular gas-gas heat exchanger to recover the waste heat of the flue gas at the outlet of the air preheater to preheat the ammonia gas to prevent secondary condensation of ammonia gas, and sending the preheated ammonia gas into an ammonia burner for combustion to replace an equal calorific value of coal, effectively reducing carbon dioxide emissions. The cooling water temperature after liquid ammonia evaporation is relatively low, and the saturated clean flue gas temperature at the outlet of the desulfurization absorption tower can be reduced through the flue gas condensation water intake device, removing the moisture in the clean flue gas, and deeply removing pollutants such as soot and SO3 in the clean flue gas. The quality of the clean flue gas condensate water is good, and after being collected by the water collecting tank and the condensation water tank, it can be used as makeup water for the desulfurization absorption tower, makeup water for circulating water, or after treatment, it can be used as washing water for the demister and makeup water for the boiler, with remarkable benefits. After the clean flue gas temperature and moisture content are reduced, it helps to reduce the white plume at the chimney outlet of the coal-fired unit, improve the image of the power plant, and reduce the impact on the urban appearance. Description of the Drawings

[0018] Figure 1 It is a schematic structural diagram of the present invention.

[0019] Among them, 1 is a coal-fired boiler, 2 is an ammonia burner, 3 is a low-temperature ammonia preheater, 4 is a dust collector, 5 is an induced draft fan, 6 is a desulfurization absorption tower, 7 is a flue gas condensation water intake device, 8 is a water collection tank, 9 is a condensate water tank, 10 is a chimney, 11 is a liquid ammonia storage tank, 12 is a liquid ammonia transfer pump, 13 is a liquid ammonia vaporizer, 14 is a cooling water circulation pump, and 15 is an electric control valve. Detailed implementation manners

[0020] In order to enable those skilled in the art of the present technology to better understand the solution of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of the embodiments, and are not intended to limit the scope of the present disclosure. In addition, in the following description, the description of well-known structures and technologies is omitted to avoid unnecessarily confusing the concepts of the present disclosure. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the scope of protection of the present invention.

[0021] The structural schematic diagrams according to the disclosed embodiments of the present invention are shown in the drawings. These figures are not drawn to scale, and for the purpose of clear expression, some details are enlarged and some details may be omitted. The shapes of various regions and layers shown in the figures, as well as their relative sizes and positional relationships, are only exemplary. In practice, there may be deviations due to manufacturing tolerances or technical limitations, and those skilled in the art can design regions / layers with different shapes, sizes, and relative positions according to actual needs.

[0022] Refer to Figure 1 , the coal-fired boiler flue gas waste heat utilization and water intake system for ammonia co-firing according to the present invention includes a coal-fired boiler 1, an ammonia burner 2, a low-temperature ammonia preheater 3, a dust collector 4, an induced draft fan 5, a desulfurization absorption tower 6, a flue gas condensation water intake device 7, a water collection tank 8, a condensate water tank 9, a chimney 10, a liquid ammonia storage tank 11, a liquid ammonia transfer pump 12, a liquid ammonia vaporizer 13, a cooling water circulation pump 14, and an electric control valve 15;

[0023] The flue gas outlet of the coal-fired boiler 1 is communicated with the flue gas inlet of the low-temperature ammonia preheater 3, the flue gas outlet of the low-temperature ammonia preheater 3 is communicated with the flue gas inlet of the dust collector 4, the flue gas outlet of the dust collector 4 is communicated with the flue gas inlet of the induced draft fan 5, the flue gas outlet of the induced draft fan 5 is communicated with the flue gas inlet of the desulfurization absorption tower 6, the flue gas outlet of the desulfurization absorption tower 6 is communicated with the flue gas inlet of the flue gas condensation water intake device 7, and the flue gas outlet of the flue gas condensation water intake device 7 is communicated with the inlet of the chimney 10.

[0024] A water collection tank 8 is provided at the bottom of the flue gas condensation water intake device 7, and the condensate outlet of the water collection tank 8 is communicated with the condensate inlet of the condensate water tank 9.

[0025] The liquid ammonia outlet of the liquid ammonia storage tank 11 is communicated with the liquid ammonia inlet of the liquid ammonia delivery pump 12, the liquid ammonia outlet of the liquid ammonia delivery pump 12 is communicated with the liquid ammonia inlet of the liquid ammonia vaporizer 13, the ammonia gas outlet of the liquid ammonia vaporizer 13 is communicated with the ammonia gas inlet of the low-temperature ammonia preheater 3, and the ammonia gas outlet of the low-temperature ammonia preheater 3 is communicated with the ammonia burner 2 on the coal-fired boiler 1.

[0026] The cooling water inlet of the liquid ammonia vaporizer 13 is communicated with the cooling water outlet of the flue gas condensation water intake device 7, the cooling water outlet of the liquid ammonia vaporizer 13 is communicated with the cooling water inlet of the cooling water circulation pump 14, and the cooling water outlet of the cooling water circulation pump 14 is communicated with the cooling water inlet of the flue gas condensation water intake device 7.

[0027] The low-temperature ammonia preheater 3 is a tubular gas-gas heat exchanger, and the heat exchange tubes in the low-temperature ammonia preheater 3 are smooth tubes. Among them, in the low-temperature ammonia preheater 3, the flue gas passes through the inside of the heat exchange tubes, and the ammonia gas passes through the outside of the heat exchange tubes. The shell and heat exchange tubes of the low-temperature ammonia preheater 3 are all made of 316L stainless steel.

[0028] The heat exchange tubes in the flue gas condensation water intake device 7 are titanium tubes with a thin wall of 0.7 mm, and the shell of the flue gas condensation water intake device 7 is made of 2205 duplex stainless steel. Among them, the cooling water passes through the inside of the heat exchange tubes, and the clean flue gas passes through the outside of the heat exchange tubes. The water collection tank 8, the condensate water tank 9 and their connected condensate water pipelines are all made of 2205 duplex stainless steel.

[0029] The clean flue gas condensate is weakly acidic, has low hardness and salt content, and has good water quality. After being collected by the water collection tank 8 and the condensate water tank 9, it is used as the makeup water for the desulfurization absorption tower 6, the makeup water for the circulating water, or after treatment, it is used as the washing water for the demister and the makeup water for the boiler.

[0030] The liquid ammonia vaporizer 13 is a shell-and-tube heat exchanger. The heat exchange tubes in the liquid ammonia vaporizer 13 are smooth tubes and are made of 316L stainless steel. The liquid ammonia passes through the inside of the heat exchange tubes, and the cooling water passes through the outside of the heat exchange tubes.

[0031] A hot water recirculation bypass is provided between the cooling water inlet and the cooling water outlet of the liquid ammonia vaporizer 13, and an electric control valve 15 is provided on the hot water recirculation bypass.

[0032] The specific working process of the present invention is as follows:

[0033] The liquid ammonia output from the liquid ammonia storage tank 11 is transported to the liquid ammonia vaporizer 13 by the liquid ammonia transfer pump 12. Using cooling water as the heat source for the evaporation and vaporization of liquid ammonia, the liquid ammonia absorbs the heat of the cooling water in the liquid ammonia vaporizer 13 and evaporates into ammonia gas. The temperature of the cooling water drops from about 40 °C to about 10 °C. Since the temperature of the ammonia gas is relatively low at this time, the ammonia gas is extremely likely to condense again, and it is necessary to preheat the ammonia gas. The ammonia gas output from the liquid ammonia vaporizer 13 enters the low-temperature ammonia preheater 3, and the waste heat of the flue gas at the outlet of the air preheater in the coal-fired boiler system is used to preheat the ammonia gas. After the temperature of the flue gas drops, it enters the dust collector 4 to improve the dust removal efficiency of the dust collector 4. The temperature of the preheated ammonia gas is about 60 °C and is sent to the ammonia burner 2 for combustion to replace the coal with the same calorific value, effectively reducing the carbon dioxide emissions.

[0034] The temperature of the cooling water output from the liquid ammonia vaporizer 13 is about 10 °C, and it is sent to the flue gas condensation water intake device 7 by the cooling water circulation pump 14 to reduce the temperature of the saturated clean flue gas at the outlet of the desulfurization absorption tower 6, remove the moisture in the clean flue gas, and deeply remove pollutants such as soot and SO3 in the clean flue gas. After the temperature and moisture content of the clean flue gas decrease, it helps to reduce the white plume at the outlet of the chimney 10. For a 300 MW coal-fired unit, when the ammonia blending ratio reaches 15% - 20%, the temperature of the clean flue gas at the outlet of the desulfurization absorption tower 6 can be reduced from about 53 °C to about 48 °C, and about 30 t / h of condensed water can be recovered. The flue gas condensation water intake system is a closed-loop system. The temperature of the cooling water at the outlet of the flue gas condensation water intake device 7 is about 40 °C and is sent back to the liquid ammonia vaporizer 13 as the heat source for ammonia vaporization. Through the electric control valve 15 on the hot water recirculation bypass, the water temperature at the inlet of the cooling water circulation pump 14 is increased to control the temperature drop of the clean flue gas in the flue gas condensation water intake device 7 from being too large.

[0035] The quality of the clean flue gas condensed water is good. After being collected by the collecting tank 8 and the condensate tank 9, it is used as makeup water for the desulfurization absorption tower 6, makeup water for the circulating water, or after treatment, it is used as the washing water for the demister and makeup water for the boiler.

Claims

1. A flue gas waste heat utilization and water intake system for a coal-fired boiler with ammonia co-firing, characterized in that, It includes a coal-fired boiler (1), an ammonia burner (2), a low-temperature ammonia preheater (3), a dust collector (4), a desulfurization absorption tower (6), a flue gas condensation water intake device (7), a water collecting tank (8), a condensate water tank (9), a chimney (10), a liquid ammonia storage tank (11), a liquid ammonia vaporizer (13), and an electric control valve (15); The flue gas outlet of the coal-fired boiler (1) is communicated with the flue gas inlet of the low-temperature ammonia preheater (3). The flue gas outlet of the low-temperature ammonia preheater (3) is communicated with the flue gas inlet of the flue gas condensation water intake device (7) via the dust collector (4) and the desulfurization absorption tower (6). The flue gas outlet of the flue gas condensation water intake device (7) is communicated with the inlet of the chimney (10); The liquid ammonia outlet of the liquid ammonia storage tank (11) is communicated with the liquid ammonia inlet of the liquid ammonia vaporizer (13). The ammonia outlet of the liquid ammonia vaporizer (13) is communicated with the ammonia inlet of the low-temperature ammonia preheater (3). The ammonia outlet of the low-temperature ammonia preheater (3) is connected to the ammonia burner (2) on the coal-fired boiler (1); The cooling water inlet of the liquid ammonia vaporizer (13) is communicated with the cooling water outlet of the flue gas condensation water intake device (7). The cooling water outlet of the liquid ammonia vaporizer (13) is communicated with the cooling water inlet of the flue gas condensation water intake device (7); A hot water recirculation bypass is arranged between the cooling water inlet and the cooling water outlet of the liquid ammonia vaporizer (13), and an electric control valve (15) is arranged on the hot water recirculation bypass; The liquid ammonia outlet of the liquid ammonia storage tank (11) is communicated with the liquid ammonia inlet of the liquid ammonia vaporizer (13) via a liquid ammonia transfer pump (12); The cooling water outlet of the liquid ammonia vaporizer (13) is communicated with the cooling water inlet of the flue gas condensation water intake device (7) via a cooling water circulation pump (14).

2. The flue gas waste heat utilization and water intake system for a coal-fired boiler with ammonia co-firing according to claim 1, characterized in that A water collecting tank (8) is arranged at the bottom of the flue gas condensation water intake device (7), and the condensate water outlet of the water collecting tank (8) is communicated with the condensate water inlet of the condensate water tank (9).

3. The flue gas waste heat utilization and water intake system for a coal-fired boiler co-firing ammonia according to claim 1, wherein The low-temperature ammonia preheater (3) is a tubular gas-gas heat exchanger, and the heat exchange tubes in the low-temperature ammonia preheater (3) are smooth tubes.

4. The flue gas waste heat utilization and water intake system for a coal-fired boiler co-firing ammonia according to claim 1, characterized in that The heat exchange tubes in the flue gas condensation water intake device (7) are made of titanium tubes.

5. The flue gas waste heat utilization and water intake system for a coal-fired boiler with ammonia co-firing according to claim 1, characterized in that, The liquid ammonia vaporizer (13) adopts a shell-and-tube heat exchanger, and the heat exchange tubes in the liquid ammonia vaporizer (13) are smooth tubes.

6. The flue gas waste heat utilization and water intake system for a coal-fired boiler with ammonia co-firing according to claim 1, wherein, The flue gas outlet of the low-temperature ammonia preheater (3) is communicated with the flue gas inlet of the flue gas condensation water intake device (7) via the dust collector (4), an induced draft fan (5), and the desulfurization absorption tower (6).

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