CN-121977223-A - Ammonia gasification and preheating system of ammonia doping boiler

CN121977223ACN 121977223 ACN121977223 ACN 121977223ACN-121977223-A

Abstract

The invention relates to the technical field of power generation, and provides an ammonia gasification and preheating system of an ammonia blending boiler, which comprises a liquid ammonia supply unit, an ammonia gasification unit and an ammonia preheating unit, wherein the liquid ammonia supply unit is used for supplying liquid ammonia and adjusting the pressure of the liquid ammonia, the ammonia gasification unit comprises an ammonia gasifier, an inlet of the ammonia gasifier is connected with an outlet of the liquid ammonia supply unit, the ammonia gasifier is configured to gasify the liquid ammonia into ammonia through exhaust steam of a steam turbine as a heat source and recover condensed water, the ammonia preheating unit comprises an air preheater and an ammonia preheater arranged behind the air preheater, the ammonia preheater is used for heating the ammonia from the ammonia gasification unit by utilizing flue gas at an outlet of the air preheater, and the preheated ammonia is conveyed to a combustor of the boiler. According to the scheme, the consumption of circulating water of the condenser and the water supplementing loss are reduced, the investment of the cooling tower is reduced, the combustion stability of ammonia entering the boiler is improved, and the consumption of fuel is reduced.

Inventors

LI ZHAOXING
ZHANG BO
XIANG XIAOFENG
ZHAO CHEN
LIU RUNMIN
WANG ZHICHAO
JIN ZHONGHUA
FANG FAN
JIA ZIXIU
LI ZONGTAI
XU DANGQI
JING XIAOLEI
ZHANG XIANGYU

Assignees

西安热工研究院有限公司

Dates

Publication Date: 20260505
Application Date: 20260107

Claims (10)

1. An ammonia gasification and preheating system of an ammonia doping boiler is characterized by comprising a liquid ammonia supply unit, an ammonia gasification unit and an ammonia preheating unit, wherein the liquid ammonia supply unit is used for supplying liquid ammonia and adjusting the pressure of the liquid ammonia, the ammonia gasification unit comprises an ammonia gasifier (3), an inlet of the ammonia gasifier (3) is connected with an outlet of the liquid ammonia supply unit, the ammonia gasifier (3) is used for gasifying the liquid ammonia into ammonia through exhaust steam of a steam turbine (5) as a heat source and recycling condensate, the ammonia preheating unit comprises an air preheater (8) arranged in a tail flue of a boiler (7) and an ammonia preheater (9) arranged behind the air preheater (8), the ammonia from the ammonia gasification unit is heated by flue gas at the outlet of the air preheater (8), and the preheated ammonia is conveyed to a combustor (6) of the boiler (7).
2. The ammonia gasification and preheating system of an ammonia doped boiler according to claim 1, wherein the steam turbine (5) is arranged between the boiler (7) and the ammonia gasifier (3), an interface above the ammonia gasifier (3) is connected with a dead steam outlet of the steam turbine (5), and a thermal well is arranged at the lower part of the ammonia gasifier (3) to collect condensed water.
3. The ammonia gasification and preheating system of the ammonia doping boiler of claim 2, wherein a condenser (4) is connected in parallel to one side of the ammonia gasification device (3), a thermal well of the ammonia gasification device (3) is connected with the thermal well of the condenser (4) through a pipeline and uniformly conveys condensed water after the two are converged through a condensed water pump, an upper interface of the condenser (4) is connected with a dead steam outlet of the steam turbine (5), and one side of the condenser (4) is also connected with a circulating water system.
4. The ammonia gasification and preheating system of an ammonia doping boiler according to claim 1, wherein the liquid ammonia supply unit comprises a liquid ammonia storage tank (1), an ammonia feeding pump (2) and a liquid ammonia throttle valve (11) which are sequentially connected, and the pressure of liquid ammonia entering the ammonia gasifier (3) is controlled to be in the range of 0.7-1.0 MPa through the ammonia feeding pump (2) and the liquid ammonia throttle valve (11).
5. An ammonia gasification and preheating system for an ammonia doped boiler according to claim 4, wherein the outlet of the ammonia gasifier (3) is connected with the ammonia side inlet of the ammonia preheater (9) through an ammonia throttle valve (10), the ammonia side outlet of the ammonia preheater (9) is connected to the burner (6), the flue gas side inlet of the ammonia preheater (9) is connected with the flue gas outlet of the air preheater (8), and the flue gas side outlet of the ammonia preheater (9) is connected with a downstream flue gas treatment device of a power plant.
6. The ammonia gasification and preheating system of an ammonia doping boiler according to claim 5, wherein the ammonia gasification device (3) comprises a shell, a heat exchange tube bundle (14) and a plurality of groups of chambers, wherein the heat exchange tube bundle (14) and the plurality of groups of chambers are arranged in the ammonia gasification device, the plurality of groups of chambers are respectively arranged at the left side and the right side of the heat exchange tube bundle (14), a three-stage ammonia outlet chamber (21), a two-stage ammonia inlet chamber (17), a gas-liquid separation descending chamber (12) and a one-stage ammonia inlet chamber (13) are sequentially arranged at one side of the ammonia gasification device, a three-stage ammonia inlet chamber (20), a two-stage ammonia outlet chamber (18) and a one-stage ammonia outlet chamber (15) are sequentially arranged at the other side of the ammonia gasification device, and the three-stage ammonia inlet chamber (20) and the three-stage ammonia outlet chamber (21), the two-stage ammonia inlet chamber (17) and the two-stage ammonia outlet chamber (18), the one-stage ammonia outlet chamber (15) and the gas-liquid separation descending chamber (12) are respectively communicated through the heat exchange tube bundle (14).
7. The ammonia gasification and preheating system of an ammonia doping boiler according to claim 6, wherein the three-stage ammonia outlet chamber (21) is connected with the ammonia throttle valve (10) outwards, one side of the secondary ammonia inlet chamber (17) is communicated with the gas-liquid separation descending chamber (12) through a secondary throttle valve (16), the gas-liquid separation descending chamber (12) is communicated with the primary ammonia inlet chamber (13) at the bottom of the gas-liquid separation descending chamber, an outlet of the gas-liquid separation descending chamber (12) is arranged at the upper part of the gas-liquid separation descending chamber (12), a liquid ammonia inlet is arranged below the outlet of the gas-liquid separation descending chamber (12), and the liquid ammonia inlet is communicated with the outlet of the ammonia feeding pump (2) through a liquid ammonia throttle valve (11).
8. The ammonia gasification and preheating system of an ammonia doping boiler according to claim 7, wherein a heat exchange tube bundle (14) of the ammonia gasification device (3) is made of stainless steel tubes or titanium tubes, exhaust steam of a steam turbine (5) flows in the shell and outside the heat exchange tube bundle (14), ammonia gas flows in the heat exchange tube bundle (14) and the cavity, the ammonia preheater (9) is a tubular gas-gas heat exchanger, the heat exchange tube in the ammonia preheater (9) is made of stainless steel tubes or titanium tubes, ammonia gas flows in the heat exchange tube, flue gas flows outside the heat exchange tube, and fins are arranged outside the heat exchange tube.
9. The ammonia and pre-heating system of an ammonia-doped boiler of claim 8, wherein the method of operating the system comprises the steps of: The ammonia mixing amount is regulated according to the unit load, the evaporation pressure of liquid ammonia entering the ammonia vaporizer (3) is controlled to be within the range of 0.7-1.0 MPa through an ammonia feeding pump (2) and a liquid ammonia throttle valve (11), so that the evaporation pressure is reduced when the ambient temperature is high, the ammonia feeding pressure is increased when the ambient temperature is low, the liquid ammonia absorbs the heat released by condensation of exhaust steam of a steam turbine (5) through multistage throttling, evaporation and overheating processes in the ammonia vaporizer (3), and the generated ammonia enters an ammonia preheater (9), exchanges heat with tail flue gas of a boiler (7), and is sent to a combustor (6) for combustion after being heated.
10. The ammonia gasification and preheating system of an ammonia-doped boiler according to claim 9, wherein the secondary throttle valve (16), the tertiary throttle valve (19) and the ammonia throttle valve (10) are in a fully opened state when the unit is in full ammonia load operation, and the secondary throttle valve (16) and the tertiary throttle valve (19) are closed to realize multi-stage throttling and cooling during low ammonia load operation, so that the condensation capacity of exhaust steam of a steam turbine (5) is enhanced, and the ammonia is prevented from being re-liquefied in a pipeline.

Description

Ammonia gasification and preheating system of ammonia doping boiler Technical Field The invention relates to the technical field of power generation, in particular to an ammonia gasification and preheating system of an ammonia doping boiler. Background The ammonia-doped combustion power generation of the coal-fired unit is one of the important technical approaches for realizing carbon emission reduction. Ammonia has a higher boiling point (-33.4 ℃) than hydrogen energy, and is easier to liquefy, store and transport, and thus has received much attention. However, ammonia fuel is typically stored and transported in liquid form with a latent heat of vaporization at atmospheric pressure as high as 1367 kJ/kg, approximately 7% of the lower heating value of ammonia. If the liquid ammonia is directly sent into a boiler for combustion, a large amount of high-grade heat in the boiler is absorbed in the gasification process, so that the combustion stability is affected, and the Yong efficiency of the boiler is reduced. Therefore, it is necessary to gasify liquid ammonia into ammonia gas in a plant to improve its combustibility and fuel calorific value. At present, the condensation of the exhaust steam of a turbine of a thermal power generating unit usually depends on a large condenser and a cooling tower, and consumes a large amount of circulating cooling water. In the prior art, patent CN114320505B provides an indirect air cooling system of an ammonia-doped power plant, and liquid ammonia gasification cold energy is utilized to cooperate with cooling circulating backwater of an indirect air cooling tower, but the system adopts an indirect heat exchange mode to absorb heat load of a condenser, so that the problems of low heat exchange efficiency and complex system exist. Another patent CN217209343U proposes to use the waste heat of the flue gas of the coal-fired boiler mixed with the ammonia gas, reduce the flue gas temperature by arranging a low Wen Anqi heater behind the air preheater, and extract the flue gas condensate by using the cold energy of liquid ammonia gasification after desulfurization. However, the method has the problem of serious corrosion of the acid condensate at the desulfurization outlet, and meanwhile, the circulating water transfers heat between the water taking device and the gasifier in a sensible heat mode, and is not matched with the gasification process temperature of the liquid ammonia at a constant temperature and a constant pressure, so that obvious Yong loss is caused. In addition, under the low-load working condition, the available heat of the flue gas is reduced, and the temperature is reduced due to expansion when the high-pressure ammonia gas enters the hearth, so that stable combustion is not facilitated. Patent CN119573414A is specially designed for a pure ammonia combustion boiler, and the condenser structure is difficult to adapt to the condensation requirement of an ammonia blending unit under the working condition of changing the ammonia blending ratio. In summary, it is necessary to develop a novel ammonia gasification and preheating system to solve the key problems that the ammonia gasification unit has not effectively solved the ammonia gasification process under the conditions of high circulating water consumption, variable load and variable ammonia doping ratio in the prior art. Disclosure of Invention In order to solve the problems in the background technology, the invention provides an ammonia gasification and preheating system of an ammonia-doped boiler, which utilizes liquid ammonia to directly cool steam turbine exhaust steam, reduces the consumption of circulating water of a condenser and water supplementing loss, reduces investment of a cooling tower, simultaneously realizes gasification of the liquid ammonia, improves the heat value of fuel entering a boiler, evaporates and preheats the ammonia, improves the combustion stability of the ammonia entering the boiler, reduces fuel consumption, can throttle in advance in low load, increases available cold and reduces expansion temperature drop of the ammonia entering the boiler. In order to achieve the above purpose, the present invention adopts the following scheme: The ammonia gasification and preheating system of the ammonia doping boiler comprises a liquid ammonia supply unit, an ammonia gasification unit and an ammonia preheating unit, wherein the liquid ammonia supply unit is used for supplying liquid ammonia and adjusting the pressure of the liquid ammonia, the ammonia gasification unit comprises an ammonia gasifier, an inlet of the ammonia gasifier is connected with an outlet of the liquid ammonia supply unit, the ammonia gasifier is configured to gasify the liquid ammonia into ammonia through exhaust steam of a steam turbine as a heat source and recover condensed water, the ammonia preheating unit comprises an air preheater arranged in a tail flue of the boiler and an ammonia preheater arranged behind the air