Energy utilization system for ammonia-blended combustion boilers

Abstract

This application relates to the field of boiler energy saving and clean combustion technology, and discloses an energy utilization system for an ammonia-blended combustion boiler. The system includes at least: an air preheater, a flue gas cooler, and a primary air heater; the flue gas discharged from the boiler is cooled by heat exchange in the flue gas cooler and then discharged into the desulfurization unit; the ammonia absorbs heat from the flue gas in the flue gas cooler and is heated before entering the ammonia burner; the secondary air is heated by heat exchange with the flue gas in the air preheater and then enters the furnace, and the air preheater is only used to heat the secondary air; the primary air does not enter the air preheater, but is heated by the primary air heater before entering the coal mill. The heat source of the primary air heater is at least one of hot water, condensate, or extracted steam. This application improves the ammonia combustion stability and the overall energy efficiency of the boiler by separating the heating paths of the primary and secondary air and combining the waste heat of the flue gas to preheat the ammonia.

Description

Technical Field

[0001] This application relates to the field of boiler energy saving and clean combustion technology, and in particular to an energy utilization system for ammonia-blended combustion boilers. Background Technology

[0002] With increasingly stringent environmental protection requirements, ammonia-blended combustion technology, as a low-carbon combustion method, is gradually being applied to coal-fired boilers. Ammonia, as a zero-carbon fuel, can effectively reduce carbon dioxide emissions through blending and can partially or completely replace carbon-based fuels for boiler combustion and power generation. However, ammonia combustion suffers from difficulties in ignition and poor combustion stability, thus placing higher demands on the heat distribution and air system temperature control of ammonia-blended combustion systems.

[0003] In addition, due to the fuel characteristics of ammonia, ammonia combustion produces a large amount of water vapor, which leads to a significant increase in flue gas volume and an increase in exhaust gas temperature compared to pure coal combustion. This reduces boiler thermal efficiency and increases fuel consumption, thereby affecting the economic efficiency of system operation.

[0004] In existing boiler systems, air preheaters are typically used to simultaneously heat primary and secondary air, utilizing waste heat from the flue gas. The existing ammonia-blended pulverized coal boiler's flue gas-air-ammonia system includes an ammonia system, an air system, and a flue gas system. In the ammonia system, ambient temperature (approximately 50°C) ammonia gas is directly fed into the boiler's ammonia burner for combustion. In the air system, cold primary and secondary air simultaneously enter the air preheater, absorbing heat from the flue gas and increasing in temperature, becoming hot primary and hot secondary air, which then exit the air preheater. The hot primary air enters the coal mill, feeding pulverized coal into the boiler's primary air burner for combustion. In the flue gas system, the flue gas generated by boiler combustion enters the air preheater, simultaneously heating the cold primary and secondary air. After releasing heat, the flue gas temperature decreases, exiting the air preheater and entering downstream flue gas treatment facilities.

[0005] Those skilled in the art will understand that, under ammonia-blended combustion conditions, the existing technical solutions have the following problems: 1. The primary air temperature is limited by the air preheater and is difficult to adjust flexibly, which is not conducive to coal grinding and combustion stability; 2. Ammonia gas directly enters the combustion system, resulting in poor combustion stability; 3. The utilization of waste heat from flue gas is at a single level, and there is still room for improvement in the overall energy efficiency of the system.

[0006] Therefore, it is necessary to provide a new energy utilization system to optimize the heat distribution of ammonia-blended combustion boilers and improve system efficiency and combustion stability. Summary of the Invention

[0007] The purpose of this application is to provide an energy utilization system for an ammonia-blended combustion boiler. This system utilizes a flue gas cooler to preheat ammonia, limits the air preheater to heating only secondary air, and simultaneously installs a separate primary air heater to heat the primary air, thus separating the heating paths for primary and secondary air. This not only improves the combustion stability of ammonia but also enhances the flexibility of primary air temperature regulation and facilitates the efficient utilization of flue gas waste heat, thereby effectively improving the overall operating efficiency of the boiler.

[0008] The embodiments of this application disclose an energy utilization system for an ammonia-blended combustion boiler, the system comprising at least: an air preheater, at least one flue gas cooler, and at least one primary air heater; The flue gas discharged from the boiler is cooled by heat exchange in the flue gas cooler and then discharged into the desulfurization device. Ammonia gas is heated by heat exchange in the flue gas cooler and then enters the ammonia burner of the boiler. Secondary air enters the air preheater and is heated by heat exchange with flue gas from the boiler before entering the furnace. The air preheater is used only to heat the secondary air. The primary air does not enter the air preheater, but is heated by the primary air heater before entering the coal mill; The heat source for the primary air heater is at least one of the following: heat transfer medium water, condensate, or extracted steam.

[0009] In another preferred embodiment, the flue gas cooler is disposed at at least one of the dust collector inlet, dust collector outlet, desulfurization device inlet, or air preheater inlet.

[0010] In another preferred embodiment, the primary air heater is one or more, and the multiple primary air heaters are arranged in series, parallel or series-parallel.

[0011] In another preferred embodiment, the system further includes a cryogenic economizer disposed in a flue gas passage downstream of the air preheater for recovering waste heat from the cryogenic flue gas from the outlet of the air preheater.

[0012] In another preferred embodiment, the system further includes a secondary air heater for preheating the secondary air before it enters the air preheater.

[0013] In another preferred embodiment, the heat source of the secondary air heater is at least one of heat transfer medium water, condensate, or extracted steam.

[0014] In another preferred embodiment, the low-temperature economizer provides heat to the primary air heater and / or the secondary air heater through a closed-loop heat medium system, which includes a heat medium water pump and a closed-loop circulation loop.

[0015] In another preferred embodiment, the flue gas cooler is used to heat ammonia using waste heat from the flue gas to improve the combustion stability of ammonia; the flue gas cooler may be one or more, and multiple flue gas coolers may be arranged in series, parallel, or series-parallel.

[0016] In another preferred embodiment, the primary air and the secondary air are independent of each other in the heating circuit.

[0017] In another preferred embodiment, the system is suitable for pulverized coal boilers or circulating fluidized bed boilers that use ammonia-infused combustion.

[0018] The main differences and effects of the implementation method of this application compared with the prior art are as follows: By using a flue gas cooler to preheat ammonia, limiting the air preheater to heating only secondary air, and simultaneously installing a separate primary air heater to heat the primary air, the heating paths for primary and secondary air are separated. This not only improves the combustion stability of ammonia but also enhances the flexibility of primary air temperature regulation and facilitates the efficient utilization of flue gas waste heat, thereby effectively improving the overall operating efficiency of the boiler.

[0019] Furthermore, preheating the ammonia gas through a flue gas cooler increases its temperature before it enters the furnace, which helps stabilize the combustion process and improves combustion stability.

[0020] Furthermore, by optimizing the air system structure, the primary air does not pass through the air preheater but is heated by an independent primary air heater, allowing the primary air temperature to be independently adjusted and improving the adaptability of coal grinding and combustion.

[0021] Furthermore, by installing a low-temperature economizer, the low-temperature flue gas from the air preheater outlet is further recycled for waste heat recovery, achieving graded utilization and improving waste heat utilization efficiency.

[0022] Furthermore, the primary and secondary air heating circuits are independent of each other, avoiding mutual interference and improving the system's adjustability and flexibility.

[0023] Furthermore, it achieves a combination of multi-stage waste heat recovery and rational heat distribution, thereby improving the overall thermal efficiency of the boiler system. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of an energy utilization system for an ammonia-blended combustion boiler according to an embodiment of this application; Figure 2 This is a schematic diagram of the structure of an energy utilization system for an ammonia-blended combustion boiler according to a preferred embodiment of the present application. Figure 3This is a schematic diagram of the structure of an energy utilization system for an ammonia-blended combustion boiler according to a preferred embodiment of the present application. Figure 4 This is a schematic diagram of the structure of an energy utilization system for an ammonia-blended combustion boiler according to a preferred embodiment of the present application. Figure 5 This is a schematic diagram of the structure of an energy utilization system for an ammonia-blended combustion boiler according to a preferred embodiment of the present application. Figure 6 This is a schematic diagram of a boiler flue gas ammonia system according to a comparative embodiment of the present application. Detailed Implementation

[0025] In the following description, numerous technical details are presented to facilitate the reader's understanding of this application. However, those skilled in the art will understand that the technical solutions claimed in the claims of this application can be implemented even without these technical details and with various variations and modifications based on the following embodiments.

[0026] Explanation of some concepts: 1. Ammonia-blended combustion: Ammonia is added as fuel to traditional coal-fired, gas-fired, or oil-fired boilers, and it participates in the boiler combustion together with the original coal, gas, or oil.

[0027] 2. Pure ammonia combustion: using ammonia as the sole fuel for boiler combustion.

[0028] In addition, in this application, heat transfer water and heat transfer circulating water have the same meaning, and closed-loop circulation and closed-loop heat transfer water system have the same meaning.

[0029] To make the objectives, technical solutions, and advantages of this application clearer, the embodiments of this application will be described in further detail below with reference to the accompanying drawings.

[0030] Embodiments of this application relate to an energy utilization system for an ammonia-blended combustion boiler. Figure 1 This is a schematic diagram of the energy utilization system used in an ammonia-blended combustion boiler.

[0031] Specifically, such as Figure 1 As shown, the energy utilization system for an ammonia-blended combustion boiler includes at least: an air preheater, at least one flue gas cooler, and at least one primary air heater.

[0032] The flue gas discharged from the boiler is cooled by heat exchange in the flue gas cooler before being discharged into the desulfurization unit.

[0033] Ammonia gas is heated by heat exchange in the flue gas cooler and then enters the ammonia burner of the boiler.

[0034] In this embodiment, the flue gas cooler is used to heat ammonia using waste heat from the flue gas, thereby improving the combustion stability of ammonia. There may be one or more flue gas coolers, arranged in series, parallel, or series-parallel configurations.

[0035] Preheating ammonia gas by using a flue gas cooler increases its temperature before it enters the furnace, which helps stabilize the combustion process and improves combustion stability.

[0036] like Figure 1 As shown, the high-temperature flue gas discharged from the boiler can first enter the flue gas cooler, or it can first enter the air preheater and then enter the flue gas cooler. That is, the flue gas in the flue gas cooler can be flue gas directly from the boiler, or it can be flue gas discharged from the boiler that has passed through the air preheater before entering the flue gas cooler. In the flue gas cooler, the flue gas exchanges heat with ammonia. Flue gas directly from the boiler enters the air preheater after passing through the flue gas cooler, and then enters the subsequent desulfurization unit after passing through the dust collector; flue gas from the air preheater enters the subsequent desulfurization unit directly after passing through the flue gas cooler and the dust collector. The ammonia absorbs heat from the flue gas in the flue gas cooler, its temperature rises, and it enters the ammonia burner in the boiler to participate in combustion.

[0037] Secondary air enters the air preheater and is heated by heat exchange with flue gas from the boiler before entering the furnace. The air preheater is used only to heat the secondary air.

[0038] The primary air does not enter the air preheater, but is heated by the primary air heater before entering the coal mill.

[0039] For example Figure 1 As shown, similarly, the flue gas in the air preheater can be directly from the boiler, or it can be flue gas discharged from the boiler, passing through a flue gas cooler before entering the air preheater. In the air preheater, the flue gas exchanges heat with secondary air. Flue gas directly from the boiler enters the flue gas cooler after passing through the air preheater, and then passes through a dust collector before entering the subsequent desulfurization unit; flue gas from the flue gas cooler passes through the air preheater and then directly passes through a dust collector before entering the subsequent desulfurization unit.

[0040] Secondary air enters the furnace after being heated by heat exchange with boiler flue gas via an air preheater. The air preheater is only used to heat the secondary air and does not participate in the heating of the primary air.

[0041] The primary air is heated by the primary air heater before entering the coal mill for coal powder drying and conveying.

[0042] The heat source for the primary air heater can be at least one of the following: heat transfer medium water, condensate, or extracted steam.

[0043] By optimizing the air system structure, the primary air does not pass through the air preheater, but is heated by an independent primary air heater, which allows the primary air temperature to be adjusted independently, improving the adaptability of coal grinding and combustion.

[0044] In this embodiment, preferably, the flue gas cooler is disposed at at least one of the dust collector inlet, dust collector outlet, desulfurization device inlet, or air preheater inlet.

[0045] The primary air heater may be one or more, and the multiple primary air heaters may be arranged in series, parallel or series-parallel.

[0046] In a further embodiment, the system further includes a low-temperature economizer disposed in a flue gas passage downstream of the air preheater for recovering waste heat from the low-temperature flue gas from the outlet of the air preheater.

[0047] By installing a low-temperature economizer, further waste heat recovery is achieved from the low-temperature flue gas at the air preheater outlet, enabling graded utilization and improving waste heat utilization efficiency.

[0048] For example Figure 1 As shown, in the case of a low-temperature economizer, the flue gas enters the low-temperature economizer via an air preheater. When the flue gas in the air preheater comes directly from the boiler, it enters the low-temperature economizer, then the flue gas cooler, and finally the dust collector before entering the subsequent desulfurization unit. When the flue gas in the air preheater is flue gas discharged from the boiler, passes through the flue gas cooler, and then enters the air preheater, it enters the low-temperature economizer, and then directly passes through the dust collector before entering the subsequent desulfurization unit.

[0049] Furthermore, preferably, the system further includes a secondary air heater for preheating the secondary air before it enters the air preheater, so as to further increase the temperature of the secondary air.

[0050] The heat source for the secondary air heater can also be at least one of the following: heat transfer medium water, condensate, or extracted steam.

[0051] Furthermore, preferably, the low-temperature economizer provides heat to the primary air heater and / or the secondary air heater through a closed-loop heat medium system, the closed-loop heat medium system including a heat medium water pump and a closed-loop circulation loop.

[0052] In this embodiment, the primary air and the secondary air are independent of each other in the heating circuit, avoiding mutual interference and improving the system's adjustability and flexibility.

[0053] It should be noted that, Figure 1The example shown only illustrates the case where there is only one flue gas cooler and one primary air heater in the system, and only uses hot water as the heating source for both the primary and secondary air heaters.

[0054] For example Figure 1 As shown, in this embodiment, the flue gas passes through a flue gas cooler, releasing heat to the ammonia; it then passes through an air preheater, releasing heat to the secondary air; and finally, it passes through a low-temperature economizer, releasing heat to the circulating heat transfer medium, water. The secondary air passes through a secondary air heater, absorbing heat and increasing its temperature before entering the air preheater. It then leaves the air preheater after absorbing heat and increasing its temperature thereafter. The air preheater only exchanges heat between the flue gas and the secondary air, without heating the primary air. The ammonia enters the flue gas cooler, absorbing heat and increasing its temperature before leaving the flue gas cooler. The primary air enters the primary air heater, absorbing heat and increasing its temperature before entering the coal mill.

[0055] In summary, this application discloses an energy utilization system for ammonia-blended combustion boilers, applicable to pulverized coal boilers or circulating fluidized bed boilers using ammonia-blended combustion. By preheating ammonia using a flue gas cooler and limiting the air preheater to heating only secondary air, while simultaneously installing a separate primary air heater to heat the primary air, the heating paths for primary and secondary air are separated. This not only improves the combustion stability of ammonia but also enhances the flexibility of primary air temperature regulation and facilitates the efficient utilization of flue gas waste heat, thereby effectively improving the overall operating efficiency of the boiler.

[0056] To better understand the technical solution of this application, several preferred embodiments of this implementation are described below. The details listed in these preferred embodiments are mainly for ease of understanding and are not intended to limit the scope of protection of this application.

[0057] Example 1: like Figure 2 As shown, this embodiment provides an energy utilization system for an ammonia-blended combustion boiler.

[0058] Flue gas from the boiler air preheater outlet passes through a low-temperature economizer and one or more flue gas coolers for cooling and heat release before entering the desulfurization absorption tower and being discharged through the chimney. The flue gas coolers are located at the dust collector inlet, and / or dust collector outlet, and / or desulfurization absorption tower inlet, and / or air preheater inlet. The low-temperature economizer is located downstream of the air preheater.

[0059] Ammonia gas at room temperature from the ammonia preparation system passes through one or more flue gas coolers, absorbing the heat released from the flue gas side. The ammonia gas temperature rises, flows out of the flue gas cooler, and enters the ammonia burner of the boiler.

[0060] The boiler's air preheater only exchanges heat between flue gas and secondary air. Cold secondary air enters the air preheater, absorbs the heat released by the flue gas, and leaves the air preheater after being heated. Alternatively, a secondary air heater can be installed at the air preheater inlet, and the cold secondary air enters the air preheater after being heated. A secondary air heater is optional. The heat source for the secondary air heater is either high-temperature circulating water from the low-temperature economizer or condensate from a stage in the power plant's condensate system.

[0061] The primary air cooling system does not employ the traditional method of heat exchange with flue gas within an air preheater. Instead, one or more primary air heaters are used to heat the primary air. After absorbing heat and increasing its temperature, the primary air enters the coal mill, which then feeds the pulverized coal into the boiler's primary air burner. Multiple primary air heaters can be arranged in series, parallel, or series-parallel configurations. The heat source for the primary air heaters is the superheat of one or more stages of extraction steam in the power plant's extraction steam system, and / or one or more stages of condensate in the power plant's condensate system, and / or high-temperature circulating water from the low-temperature economizer.

[0062] When the heat source for the primary or secondary air heater is circulating hot water, a low-temperature economizer is installed downstream of the boiler air preheater. Flue gas enters the low-temperature economizer, releases heat, and cools before exiting. A closed-loop hot water system is established, comprising a hot water pump, a low-temperature economizer, a primary air heater, and / or a secondary air heater. The low-temperature water, pressurized by the hot water pump, flows into the low-temperature economizer, where it transfers the heat released by the flue gas to the hot water, raising its temperature to high-temperature water before exiting. The high-temperature water from the low-temperature economizer outlet flows into the primary and / or secondary air heaters, where it releases heat to cool the cold air before becoming low-temperature water and entering the hot water pump. The hot water circulates within the system to achieve heat transfer.

[0063] The medium flowing into the low-temperature economizer to absorb heat from the flue gas side can be either circulating heat transfer water or condensate from the power plant's condensate system. Condensate from the power plant's condensate system enters the low-temperature economizer, absorbs the heat released from the flue gas side, raises its temperature, flows out of the low-temperature economizer, and returns to the condensate system.

[0064] This embodiment is an overall design scheme for an energy utilization system for an ammonia-infused combustion boiler.

[0065] Example 2: like Figure 3 As shown, this embodiment provides an energy utilization system for an ammonia-blended combustion boiler.

[0066] Flue gas from the boiler air preheater outlet is cooled and released by the flue gas cooler before entering the desulfurization absorption tower and being discharged through the chimney. The flue gas cooler is located at the inlet of the dust collector.

[0067] Ammonia gas at room temperature from the ammonia preparation system passes through a flue gas cooler, absorbs the heat released from the flue gas side, and its temperature rises. The ammonia gas then flows out of the flue gas cooler and into the ammonia burner of the boiler.

[0068] The boiler's air preheater only exchanges heat between flue gas and secondary air. Cold secondary air enters the air preheater, absorbs the heat released by the flue gas, and leaves the air preheater after being heated.

[0069] The primary air cooling system does not employ the traditional method of heat exchange with flue gas within an air preheater. Instead, it uses three primary air heaters to heat the primary air. After absorbing heat and reaching a higher temperature, the primary air enters the coal mill, which then feeds the pulverized coal into the boiler's primary air burner. The three primary air heaters are arranged in series. The heat source for primary air heaters 2 and 3 is the superheat of one or more stages of extraction steam in the power plant's extraction steam system, while the heat source for primary air heater 1 is the condensate from one or more stages of the power plant's condensate system.

[0070] Compared with Example 1, this example uses a single flue gas cooler and three primary air heaters connected in series, which simplifies the structure and achieves basic energy utilization optimization while ensuring ammonia preheating and air system separation.

[0071] Example 3: like Figure 4 As shown, this embodiment provides an energy utilization system for an ammonia-blended combustion boiler.

[0072] Flue gas from the boiler air preheater outlet passes through a low-temperature economizer and two flue gas coolers for cooling and heat release before entering the desulfurization absorption tower and being discharged through the chimney. The flue gas coolers are located at the inlet of the dust collector, the inlet of the desulfurization absorption tower, and / or the inlet of the air preheater. The low-temperature economizer is located downstream of the air preheater.

[0073] Ammonia gas at room temperature from the ammonia preparation system passes through two flue gas coolers, absorbing the heat released from the flue gas side. The ammonia gas temperature rises, flows out of the flue gas coolers, and enters the ammonia burner of the boiler.

[0074] The boiler's air preheater only exchanges heat between flue gas and secondary air. Secondary air enters the air preheater, absorbs the heat released by the flue gas, and leaves the air preheater after being heated. A secondary air heater is installed at the air preheater inlet; the cold secondary air enters the air preheater after being heated. The heat source for the secondary air heater is high-temperature circulating water from the low-temperature economizer.

[0075] The primary air cooling system does not employ the traditional method of heat exchange with flue gas within an air preheater. Instead, three primary air heaters heat the primary air. After absorbing heat and reaching a higher temperature, the primary air enters the coal mill, which then feeds the pulverized coal into the boiler's primary air burner. The three primary air heaters are arranged in series and parallel. The heat source for primary air heaters 2 and 3 is the superheat of one or more stages of extraction steam in the power plant's extraction steam system, while the heat source for primary air heater 1 is condensate from one stage of the power plant's condensate system.

[0076] The heat source for the secondary air heater is circulating hot water. A low-temperature economizer is installed downstream of the boiler air preheater. Flue gas enters the low-temperature economizer, releases heat, and cools before flowing out. A closed-loop hot water system is set up, which includes a hot water pump, a low-temperature economizer, and a secondary air heater. The low-temperature water, pressurized by the hot water pump, flows into the low-temperature economizer. The economizer transfers the heat released by the flue gas to the hot water, raising its temperature to high-temperature water, which then flows out of the low-temperature economizer. The high-temperature water at the outlet of the low-temperature economizer flows into the secondary air heater, where it releases heat to cool the cold air, becoming low-temperature water before entering the hot water pump.

[0077] Compared with Example 1, this example uses two flue gas coolers to heat ammonia and a closed-loop hot water system to provide a heat source for the secondary air heater, further optimizing waste heat utilization and the structure of the air system.

[0078] Example 4: like Figure 5 As shown, this embodiment provides an energy utilization system for an ammonia-blended combustion boiler.

[0079] Flue gas from the boiler air preheater outlet passes through a low-temperature economizer and two flue gas coolers for cooling and heat release before entering the desulfurization absorption tower and being discharged through the chimney. The flue gas coolers are located at the inlet of the dust collector and the inlet of the desulfurization absorption tower. The low-temperature economizer is located downstream of the air preheater.

[0080] Ammonia gas at room temperature from the ammonia preparation system passes through two flue gas coolers, absorbing the heat released from the flue gas side. The ammonia gas temperature rises, flows out of the flue gas coolers, and enters the ammonia burner of the boiler.

[0081] The boiler's air preheater only exchanges heat between flue gas and secondary air. Secondary air enters the air preheater, absorbs the heat released by the flue gas, and leaves the air preheater after being heated. A secondary air heater is installed at the air preheater inlet; the cold secondary air enters the air preheater after being heated. The heat source for the secondary air heater is condensate from a stage in the power plant's condensate system.

[0082] The primary air cooling process does not employ the traditional method of heat exchange with flue gas within an air preheater. Instead, two primary air heaters are used to heat the primary air. After absorbing heat and reaching a higher temperature, the primary air enters the coal mill, which then feeds the pulverized coal into the boiler's primary air burner. The two primary air heaters are arranged in series. The heat source for primary air heater 2 is the superheat of a stage of steam extracted from the power plant's extraction steam system, while the heat source for primary air heater 1 is condensate from a stage of condensate in the power plant's condensate system.

[0083] The medium flowing into the low-temperature economizer to absorb heat from the flue gas side is condensate from the power plant's condensate system. Condensate from the power plant's condensate system enters the low-temperature economizer, absorbs the heat released from the flue gas side, raises its temperature, flows out of the low-temperature economizer, and returns to the condensate system.

[0084] Compared with Example 1, this embodiment uses condensate as the main waste heat utilization medium.

[0085] In summary, this application proposes an energy coupling and utilization system for flue gas, ammonia, air, steam, and water, which can improve boiler combustion, increase boiler efficiency, and enhance boiler performance. It is suitable for ammonia-blended combustion boilers, and the main technical solutions include: 1) The system may include: an air preheater, a flue gas cooler, a low-temperature economizer, a primary air heater, a secondary air heater, and a heat transfer medium pump.

[0086] 2) The flue gas passes through the flue gas cooler and releases heat to the ammonia gas, the flue gas passes through the air preheater and releases heat to the secondary air, and the flue gas passes through the low-temperature economizer and releases heat to the circulating heat transfer medium water or condensate.

[0087] 3) The secondary air passes through the secondary air heater, absorbs heat to increase its temperature, and then enters the air preheater. It absorbs heat to increase its temperature again in the air preheater before leaving. The air preheater only exchanges heat between the flue gas and the secondary air; it does not heat the primary air.

[0088] 4) The primary air enters the primary air heater, absorbs heat and is heated before entering the coal mill.

[0089] 5) Ammonia enters the flue gas cooler, absorbs heat and increases in temperature before leaving the flue gas cooler.

[0090] 6) A closed-loop hot water system is adopted. The heat absorbed from the flue gas side is used to heat the hot water. The low-temperature hot water is heated to become high-temperature hot water. The high-temperature hot water is then used to release heat to the cold primary air and / or cold secondary air. After releasing heat, the high-temperature hot water becomes low-temperature hot water and returns to the flue gas side to absorb heat.

[0091] 7) There may be one or more flue gas coolers. Multiple flue gas coolers may be arranged in series, parallel, or series-parallel. The flue gas coolers may be located at the inlet of the dust collector, and / or the outlet of the dust collector, and / or the inlet of the desulfurization absorption tower, and / or the inlet of the air preheater.

[0092] 8) The heat source for the secondary air heater is either the high-temperature heat transfer fluid circulating water from the low-temperature economizer or the condensate from a stage in the power plant's condensate system. A secondary air heater may or may not be installed.

[0093] 9) The heat source for the primary air heaters is the superheat of one or more stages of extraction steam in the power plant's extraction steam system, and / or one or more stages of condensate in the power plant's condensate system, and / or high-temperature heat transfer fluid circulating water from the low-temperature economizer. There may be one or more primary air heaters. Multiple primary air heaters may be arranged in series, parallel, or series-parallel configurations.

[0094] 10) The medium flowing into the low-temperature economizer to absorb heat from the flue gas side can be heat transfer circulating water or condensate from the power plant's condensate system. A low-temperature economizer may or may not be installed.

[0095] 11) This system can be used in pulverized coal boilers or circulating fluidized bed boilers with ammonia combustion.

[0096] The technical solution of this application utilizes the flue gas emitted from the boiler to heat ammonia, transferring the heat of the originally emitted flue gas to the ammonia. The energy that was originally wasted is recovered through the combustion of ammonia in the boiler, thereby improving boiler efficiency, reducing the consumption of ammonia and other fuels such as coal, and reducing the emission of pollutants and carbon dioxide in the flue gas, while also reducing the operating costs of the power plant.

[0097] For boilers with a high proportion of ammonia blending, the number of coal mills in operation is smaller, resulting in a corresponding reduction in the required primary air volume. This significantly reduces the heat input needed on the primary air side, allowing the primary air to be heated separately using the heat from condensate or the superheated section of the extraction steam in the power plant's thermal system. Compared to traditional technologies, the primary air does not enter the air preheater, greatly reducing air leakage in the preheater and lowering the operating power consumption of the primary air fan and induced draft fan, thereby reducing the power plant's operating costs.

[0098] To further illustrate the beneficial effects of this application, a comparative embodiment is provided below. Figure 6 This is a schematic diagram of the structure of the comparative embodiment.

[0099] like Figure 6 As shown, in this comparative embodiment, the conventional air heating method of a coal-fired boiler is used, where the air preheater heats both primary and secondary air simultaneously. The flue gas discharged from the boiler sequentially enters the air preheater, exchanges heat with the primary and secondary air, and is then discharged from the system. The primary air, heated by the air preheater, enters the coal mill, while the secondary air, heated by the air preheater, enters the furnace for combustion.

[0100] In this system, ammonia gas is not preheated by a flue gas cooler, but enters the burner directly to participate in combustion.

[0101] Under the same boiler load and the same ammonia blending ratio, comparing the embodiments of this application with the comparative embodiment reveals the following differences: 1. Regarding combustion stability: In the comparative example, the ammonia gas was not preheated, resulting in a lower temperature when it entered the furnace and a slower combustion reaction rate, which could easily lead to unstable combustion or reduced burnout. In contrast, this application preheats the ammonia gas using a flue gas cooler, thereby improving the reactivity of the ammonia gas and making the combustion more stable.

[0102] 2. Primary air regulation capacity: In the comparative embodiment, both primary air and secondary air rely on air preheaters for heating, and the two are coupled in the same heat exchange device, making it difficult to independently adjust the temperature of the primary air. However, this application sets up an independent primary air heater, which allows the temperature of the primary air to be flexibly adjusted according to the operating requirements of the coal mill, thereby improving the system adaptability.

[0103] 3. Regarding waste heat utilization efficiency: In the comparative embodiments, the waste heat of flue gas is mainly utilized in the air preheater, and the level of waste heat utilization is relatively simple; while in this application, through devices such as flue gas coolers and low-temperature economizers, the waste heat of flue gas is recovered and utilized in stages, thereby improving the overall thermal efficiency of the system.

[0104] 4. Smoke exhaust temperature and economic efficiency: In the comparative embodiments, due to the lack of further recovery of waste heat from low-temperature flue gas, the flue gas temperature is relatively high and the boiler efficiency is relatively low. For example, compared with a boiler that burns only bituminous coal, when the ammonia blending ratio reaches 60%, the flue gas temperature of the boiler in the comparative embodiments can increase from about 114°C to about 140°C, and the boiler efficiency can decrease from about 95.1% to about 93.35%. However, this application can effectively reduce the flue gas temperature of the boiler, increase the boiler efficiency, improve the boiler performance, reduce the consumption of ammonia and coal, and improve the economic efficiency of operation through multi-stage waste heat utilization.

[0105] In summary, compared with the comparative embodiments, this application significantly improves combustion stability, system regulation capability and energy utilization efficiency through technical means such as ammonia preheating, separation of primary and secondary air heating paths, and graded utilization of flue gas waste heat.

[0106] It should be noted that the components or devices mentioned in the embodiments of this application are all logical modules. Physically, a logical module can be a physical module, a part of a physical module, or a combination of multiple physical modules. The physical implementation of these logical modules themselves is not the most important factor; rather, the combination of functions implemented by these logical modules is the key to solving the technical problem proposed in this application. Furthermore, to highlight the innovative aspects of this application, the above-described system embodiments have not introduced components or devices that are not closely related to solving the technical problem proposed in this application. This does not mean that other components or devices do not exist in the above embodiments.

[0107] It should be noted that in the claims and specification of this patent, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one" does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0108] Although this application has been illustrated and described with reference to certain preferred embodiments thereof, those skilled in the art should understand that various changes in form and detail may be made thereto without departing from the spirit and scope of this application.

Claims

1. An energy utilization system for an ammonia-blended combustion boiler, characterized in that, The system includes at least: an air preheater, at least one flue gas cooler, and at least one primary air heater; The flue gas discharged from the boiler is cooled by heat exchange in the flue gas cooler and then discharged into the desulfurization device. Ammonia gas is heated by heat exchange in the flue gas cooler and then enters the ammonia burner of the boiler. Secondary air enters the air preheater and is heated by heat exchange with flue gas from the boiler before entering the furnace. The air preheater is used only to heat the secondary air. The primary air does not enter the air preheater, but is heated by the primary air heater before entering the coal mill; The heat source for the primary air heater is at least one of the following: heat transfer medium water, condensate, or extracted steam.

2. The energy utilization system for an ammonia-blended combustion boiler according to claim 1, characterized in that, The flue gas cooler is installed at at least one of the following: dust collector inlet, dust collector outlet, desulfurization unit inlet, or air preheater inlet.

3. The energy utilization system for an ammonia-blended combustion boiler according to claim 1, characterized in that, The primary air heater may be one or more, and the multiple primary air heaters may be arranged in series, parallel or series-parallel.

4. The energy utilization system for an ammonia-blended combustion boiler according to claim 1, characterized in that, The system also includes a low-temperature economizer, which is located in the flue gas passage downstream of the air preheater and is used to recover waste heat from the low-temperature flue gas from the outlet of the air preheater.

5. The energy utilization system for an ammonia-blended combustion boiler according to claim 4, characterized in that, The system also includes a secondary air heater for preheating the secondary air before it enters the air preheater.

6. The energy utilization system for an ammonia-blended combustion boiler according to claim 5, characterized in that, The heat source for the secondary air heater is at least one of the following: heat transfer medium water, condensate, or extracted steam.

7. The energy utilization system for an ammonia-blended combustion boiler according to claim 5, characterized in that, The low-temperature economizer provides heat to the primary air heater and / or the secondary air heater through a closed-loop heat medium system, which includes a heat medium water pump and a closed-loop circulation circuit.

8. The energy utilization system for an ammonia-blended combustion boiler according to claim 1, characterized in that, The flue gas cooler is used to heat ammonia using waste heat from the flue gas, thereby improving the combustion stability of ammonia. There are one or more flue gas coolers, and multiple flue gas coolers are arranged in series, parallel, or series-parallel configurations.

9. The energy utilization system for an ammonia-blended combustion boiler according to claim 1, characterized in that, The primary air and the secondary air are independent of each other in the heating circuit.

10. The energy utilization system for an ammonia-blended combustion boiler according to claim 1, characterized in that, The system is suitable for pulverized coal boilers or circulating fluidized bed boilers that use ammonia-infused combustion.

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