CN-121977204-A - Emission reduction system of circulating fluidized bed boiler, control method and control unit thereof

CN121977204ACN 121977204 ACN121977204 ACN 121977204ACN-121977204-A

Abstract

The invention provides an emission reduction system of a circulating fluidized bed boiler, a control method and a control unit thereof, and relates to the technical field of industrial boilers. The system comprises a circulating fluidized bed boiler, a carbon trapping system, a purified flue gas recirculation loop and a control unit, wherein an inlet of the carbon trapping system is connected with a flue at the tail part of the boiler, an inlet of the purified flue gas recirculation loop is connected with a purified flue gas outlet of the carbon trapping system, an outlet of the purified flue gas recirculation loop is connected with an air inlet system or a combustion area of a hearth of the boiler body, and the control unit is respectively connected with a sensor at the side of the boiler and a sensor at the side of the carbon trapping system in a signal manner. The invention takes the purified flue gas after carbon dioxide removal as a recycling medium, avoids the dilution effect of the traditional scheme on the carbon dioxide concentration at the inlet of the carbon capture system, reduces the energy consumption of carbon capture and regeneration, realizes the integral optimization of boiler combustion and the carbon capture system, and improves the economical efficiency and the operation flexibility of the whole system on the premise of meeting the NOx emission constraint.

Inventors

TANG GUOAN
WANG XIN
HE JIANLE
TANG XIUNENG
WANG WENYU
LIANG XIUJIN
HUANG JIANPING
LIU FAZHI
Lv Buchu
ZHOU XIAOMING

Assignees

华电电力科学研究院有限公司

Dates

Publication Date: 20260505
Application Date: 20260330

Claims (10)

1. An emission abatement system for a circulating fluidized bed boiler, comprising: A circulating fluidized bed boiler (1); The inlet of the carbon trapping system is connected with the tail flue of the boiler and is used for trapping carbon dioxide in the flue gas; The inlet of the purified flue gas recirculation loop is connected with a purified flue gas outlet of the carbon trapping system, and the outlet of the purified flue gas recirculation loop is connected with an air inlet system or a hearth combustion zone of the circulating fluidized bed boiler (1); And the control unit (51) is respectively connected with the boiler side sensor and the carbon capture system side sensor in a signal manner and is used for dynamically adjusting the recirculation amount of the purified flue gas according to the boiler operation parameters and the carbon capture system operation parameters so as to realize bidirectional cooperative control with the aim of lowest total operation cost of the whole system.
2. The circulating fluidized bed boiler abatement system of claim 1, further comprising: The inlet of the original flue gas recirculation loop is connected with the back of the boiler tail flue dust remover (3) and the front of the carbon trapping system inlet, and the outlet of the original flue gas recirculation loop is connected with an air inlet system or a hearth combustion zone of the circulating fluidized bed boiler (1); The purified flue gas recirculation loop is arranged in parallel with the raw flue gas recirculation loop.
3. The circulating fluidized bed boiler emission reduction system of claim 2, wherein a first control valve (91) is provided on the cleaned flue gas recirculation loop; A second control valve (92) is arranged on the raw flue gas recirculation loop; the first control valve (91) and the second control valve (92) are used for independently controlling the recirculation flow of two paths of flue gas.
4. The circulating fluidized bed boiler abatement system of claim 1, wherein the outlet of the cleaned flue gas recirculation loop comprises: the first outlet is connected to the primary air chamber of the boiler and is used for being mixed with primary air and entering the hearth through the air distribution plate; And/or a second outlet which extends into the dense-phase zone or the combustion high-temperature zone of the hearth through a special nozzle (33) and is used for directly injecting purified flue gas into the combustion reaction zone.
5. The circulating fluidized bed boiler emission reduction system of claim 1, wherein the control unit (51) comprises: The data acquisition module is used for acquiring real-time operation data including boiler load, bed temperature, hearth outlet oxygen, NOx concentration, carbon capture system inlet CO 2 concentration, absorbent circulation amount and regeneration tower steam consumption; The calculation module is internally provided with an optimization algorithm taking the lowest total running cost of the whole system as an objective function and taking the NOx emission concentration and the CO 2 trapping rate as constraint conditions, and is used for calculating the optimal purified flue gas recirculation amount and the carbon trapping system running set value; and the instruction output module is used for sending an adjusting instruction to the recirculation fan, the control valve and the carbon capture system executing mechanism.
6. A control method of an emission reduction system of a circulating fluidized bed boiler, applied to the system of any one of claims 1 to 5, characterized by comprising the steps of: Leading out the purified flue gas from the outlet of the carbon trapping system after removing most of carbon dioxide; after the purified flue gas is pressurized, the purified flue gas is introduced into a primary air system of a circulating fluidized bed boiler or is directly sprayed into a combustion zone of a hearth; Acquiring boiler operation parameters and carbon capture system operation parameters in real time; the total operation cost of the boiler-carbon capture whole system is taken as an optimization target, the recirculation quantity of purified flue gas is dynamically regulated, and the operation working conditions of the carbon capture system are cooperatively regulated, so that the system operates at an optimal working condition point on the premise of meeting the requirements of NOx emission limit and CO 2 capture rate.
7. The control method of the emission reduction system of the circulating fluidized bed boiler according to claim 6, wherein the optimization objective of the total operation cost of the whole system is the lowest, and the cost function is as follows: Wherein, the For the total operating cost of the system, For the steam price conversion factor to be used, For the coefficient of the conversion of the electricity price, The energy consumption for the regeneration of the carbon capture system, For the purpose of carbon capture efficiency, Is the split ratio of the flue gas, For the total power consumption of the recirculating fan, Is the recycling quantity of the raw flue gas, In order to purify the amount of flue gas recirculation, For the NOx emissions to exceed the penalty factor, In order to achieve an actual NOx emission concentration, Is the discharge concentration limit.
8. The control method of emission reduction system of circulating fluidized bed boiler according to claim 6, wherein in the step of introducing primary air system of circulating fluidized bed boiler or directly spraying into combustion zone of furnace, the volume fraction of oxygen in the purified flue gas introduced into furnace The determination is made according to the following formula: Wherein, the Is the dry basis volume fraction of oxygen in the raw flue gas, Is the dry basis volume fraction of carbon dioxide in the raw flue gas, Is the removal efficiency of the carbon capture system.
9. The method according to claim 6, wherein the primary air system of the circulating fluidized bed boiler is introduced or directly injected into the combustion zone of the furnace, and the purified flue gas is mixed with the primary air and then fed into the target oxygen volume fraction before the furnace The following relationship is satisfied: Wherein, the For the volume flow of fresh air, Is the volume fraction of oxygen in the air, The flow rate is recycled for the flue gas which is not decarbonized, For the volume fraction of oxygen in the flue gas which is not decarbonized, In order to purify the flow of the flue gas recirculation, To purify the oxygen volume fraction in the flue gas.
10. A control unit for performing the circulating fluidized bed boiler emission reduction system control method of any one of claims 6 to 9, comprising: A processor; A memory for storing one or more programs; The one or more programs, when executed by the one or more processors, cause the one or more processors to perform the functions of dynamically adjusting the amount of purified flue gas recirculation and cooperatively controlling the operating conditions of the carbon capture system with the goal of minimizing the total operating cost of the boiler-carbon capture overall system.

Description

Emission reduction system of circulating fluidized bed boiler, control method and control unit thereof Technical Field The invention relates to the technical field of industrial boilers, in particular to a circulating fluidized bed boiler emission reduction system, a control method and a control unit thereof. Background The circulating fluidized bed boiler has become an important device in the fields of coal-fired power generation and industrial heat supply because of the advantages of wide fuel adaptability, high combustion efficiency, controllable pollutant emission and the like. In the prior art, in order to reduce NOx emissions from circulating fluidized bed boilers, flue gas recirculation techniques are commonly employed. The technology generally leads out a part of low-temperature raw flue gas from a boiler tail flue (positioned behind a dust remover), and the low-temperature raw flue gas is sent back to a furnace chamber to participate in combustion after being pressurized by a recirculation fan. The return air supply is mainly characterized in that the return air supply is firstly supplied to an air chamber at the bottom of a hearth and enters the hearth through an air distribution plate after being mixed with primary air, the proportion of secondary air is increased by replacing part of the primary air with low-oxygen flue gas under the condition that the total air quantity is unchanged, the air staged combustion is enhanced, the oxygen concentration and the temperature of a dense-phase area are reduced, and the return air supply is directly supplied to a combustion high-temperature area of the hearth through a special nozzle, so that the recirculated flue gas acts on the high-temperature reaction area rapidly and uniformly through reasonably arranged nozzles, and the oxygen concentration of the area is directly diluted. However, the existing flue gas recirculation technology recirculates raw flue gas of high-concentration carbon dioxide back to the furnace, so that the concentration of carbon dioxide in flue gas entering a carbon capture system is diluted, the running energy consumption of the carbon capture system is high, a unified collaborative optimization mechanism is lacking, and the technical problem that the overall collaborative optimization of the energy efficiency and the cost of the whole system can not be realized while the NOx emission constraint is met is solved. Disclosure of Invention The invention aims to provide an emission reduction system of a circulating fluidized bed boiler, which is used for solving the technical problems that in the prior art, in the existing flue gas recirculation technology, the operation energy consumption of a carbon trapping system is high, a unified collaborative optimization mechanism is lacked, and the overall collaborative optimization of the energy efficiency and the cost of the whole system can not be realized while the NOx emission constraint is met. In a first aspect, the invention provides an emission reduction system of a circulating fluidized bed boiler, which comprises the circulating fluidized bed boiler, a carbon capture system, a purified flue gas recirculation loop and a control unit. The inlet of the carbon trapping system is connected with the tail flue of the boiler and is used for trapping carbon dioxide in the flue gas. The inlet of the purified flue gas recirculation loop is connected with the purified flue gas outlet of the carbon trapping system, and the outlet is connected with the air inlet system or the hearth combustion zone of the circulating fluidized bed boiler. The control unit is respectively connected with the boiler side sensor and the carbon capture system side sensor in a signal manner and is used for dynamically adjusting the recirculation quantity of purified flue gas according to the boiler operation parameters and the carbon capture system operation parameters so as to realize bidirectional cooperative control with the minimum total operation cost of the whole system as a target. Further, the circulating fluidized bed boiler emission reduction system further comprises: And the inlet of the raw flue gas recirculation loop is connected with the back of the boiler tail flue dust remover and the front of the inlet of the carbon trapping system, and the outlet of the raw flue gas recirculation loop is connected with an air inlet system or a hearth combustion zone of the circulating fluidized bed boiler. The purified flue gas recirculation loop is arranged in parallel with the raw flue gas recirculation loop. Further, a first control valve and a second control valve are respectively arranged on the purified flue gas recirculation loop and the raw flue gas recirculation loop and are used for independently controlling the recirculation flow of the two paths of flue gas. Further, the outlet of the cleaned flue gas recirculation circuit comprises a first outlet and/or a second outlet. The first outlet is connected to the