SNCR (selective non-catalytic reduction) zoning system suitable for circulating fluidized bed boiler under deep peak regulation transformation

Abstract

The utility model discloses a circulating fluidized bed boiler SNCR (selective non-catalytic reduction) zoning system applicable to deep peak regulation transformation, which comprises two boilers, each boiler is provided with two separators, each separator is provided with 40 spray guns 1, the spray gun 1 at each separator is provided with a flow regulating valve, and the flow regulating valves are connected with the two boilers. The spray gun 1 is also provided with a valve and a metal rotor flow meter; each boiler is provided with an ammonia water storage tank which is independently used; the four separators and the hearth part are controlled in a partitioned manner, upper and lower reaction parts are controlled in a partitioned manner through parameters such as combustion temperature, and the four separators and the left and right hearth parts are controlled in a partitioned manner through a conveying system and a valve; the left hearth and the right hearth of the boiler are separately controlled according to coal quality change, combustion degree and extreme conditions during operation, and a denitration system is adjusted in a targeted manner, so that NOX emission is economically, effectively and stably reduced.

Description

TECHNICAL FIELD

[0001] The utility model belongs to the field of coal-fired power plant flue gas denitration technology, in particular, relate to the SNCR partition system suitable for the circulating fluidized bed boiler under the deep peak shaving reconstruction. BACKGROUND

[0002] With the development of new energy power generation, it brings new opportunities for the research of traditional coal-fired power plant boiler low load operation technology, which puts forward higher requirements for the standard emission of pollutants in boiler low load operation flue gas, the economic and reliable operation of environmental protection device. Whether from the perspective of national "double carbon" target, or from the social and economic benefits, the research and development of boiler flue gas pollutant standard emission technology under deep peak shaving has great significance.

[0003] The circulating fluidized bed (CFB) boiler has the characteristics of wide fuel adaptability, low gaseous pollutant emission and strong low load stable combustion, but due to the use of selective non-catalytic reduction (SNCR) for denitration, when participating in deep peak shaving operation, the temperature of the boiler decreases, which leads to the temperature of the separator inlet flue gas denitration reaction zone being lower than the optimal reaction temperature of SNCR, the stability of ultra-low control of nitrogen oxides is poor, which cannot meet the requirements of ultra-low emission of nitrogen oxides in flue gas, the consumption of denitration reductant increases, and the existing circulating fluidized bed boiler SNCR denitration system cannot meet the requirements of ultra-low emission of nitrogen oxides in flue gas, so the existing denitration system needs to be optimized and transformed.

[0004] The Chinese patent with the authorization announcement number CN205598926U discloses a circulating fluidized bed boiler flue gas SNCR and SCR coupling denitration device, the flue gas containing nitrogen oxides first carries out SNCR denitration reaction in the flue of the cyclone separator, removes part of the nitrogen oxides, and then enters the catalyst device of the SCR, further removes the nitrogen oxides, and the reaction treated flue gas enters the air preheater. The denitration efficiency of the circulating fluidized bed boiler flue gas SNCR and SCR coupling denitration device can reach more than 80%, which can realize ultra-low emission of nitrogen oxides, the ammonia escape is less than 3ppm, the production amount of ammonium bisulfate is low, it is not easy to cause the air preheater to be blocked or corroded, the system pressure loss is small, and the catalyst replacement cost is low.

[0005] The above technical scheme has the following defects:

[0006] The number of each boiler used spray gun 1 is the same as the traditional one (more than 24), in the case of high ammonia water consumption and large nitrogen oxide fluctuation, it is impossible to realize ultra-low emission of nitrogen oxides, the ammonia water solution and the dilution water of the two boilers adopt a single mother pipe, which cannot realize the separate control of the denitration system of a single furnace, in the case of large deviation of the load and combustion condition of the two furnaces, it is impossible to accurately control the emission of nitrogen oxides, and due to the reduction of ultra-low NOx emission limit, more ammonia water is needed to participate in the reaction. Utility model content

[0007] In view of the above defects, the utility model provides suitable for depth peak shaving reconstruction under circulating fluidized bed boiler SNCR partition system, including two boilers, two the boiler is installed with two separators respectively;

[0008] Each the separator is installed with 40 branch lances 1, forms an independent spraying area;

[0009] The lance 1 at each the separator place is controlled uniformly by flow regulating valve, and the lance 1 is also installed with valve to carry out independent control, and is measured by the metal rotor flowmeter installed;

[0010] Two the boiler is equipped with the conveying system for ammonia water solution and dilute water conveying separately used;

[0011] Each the boiler is equipped with the ammonia water storage tank separately used.

[0012] Further, the position of the lance 1 is determined by numerical simulation calculation to the flue gas flow and NOX concentration in the separator inlet flue.

[0013] Further, the lance 1 is equipped with three inlets respectively for ammonia water solution, atomization blowing wind and jacket cooling wind conveying.

[0014] Further, the lance 1 is composed of solution pipe, nozzle, atomization air pipe, cooling air pipe and support structure, and the nozzle is composed of liquid cap, external thread joint, air cap and spout.

[0015] The utility model has the following beneficial effects compared with prior art:

[0016] 1, by adding the number of lance 1 and the determination of lance 1 installation position, reach the purpose that reducing agent and NOX in flue gas are fully mixed, and effectively reduce the consumption of reducing agent;

[0017] 2, add ammonia water storage tank can realize ammonia water storage quantity to meet the requirement of unit operation;

[0018] 3. According to the arrangement of the conveying system in each independent area, the four separators are divided into subareas with the furnace part, the upper and lower reaction parts are controlled by parameters such as combustion temperature, and the four separators and the left and right furnace parts are controlled by the conveying system and valves, the SNCR reaction part is added in the furnace under low load, the left and right furnace parts are controlled separately according to the change of coal quality, the degree of combustion and extreme conditions during operation, the denitration system is adjusted in a targeted manner, thereby realizing economic, effective and stable reduction of NOx emission, the denitration system is adjusted in a targeted manner through the subarea control of each denitration reaction area, under the "double carbon" target, the thermal power generation enterprise can meet the requirements of deep peak shaving and stable operation, and the minimum amount of denitration reagent can be used under the ultra-low emission transformation, thereby realizing economic, effective and stable reduction of NOx emission. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 It is a schematic diagram of the whole area system in the utility model.

[0020] Figure 2 It is a schematic diagram of the subarea system in the utility model.

[0021] Figure 3 It is a connection schematic diagram of the lance in the utility model.

[0022] In the figure: 1, lance. DETAILED DESCRIPTION

[0023] In order to facilitate the understanding of the utility model, the device of the utility model will be described more fully below with reference to the relevant drawings. The embodiments of the device are shown in the drawings. However, the device can be realized in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the utility model more thorough and comprehensive.

[0024] In the description of the utility model, it should be pointed out that, unless otherwise explicitly specified and limited, the terms "mounting", "connection", "setting" should be understood broadly, for example, it can be fixedly connected, set, or detachably connected, set, or integrally connected, set. For ordinary skilled persons in the art, the specific meaning of the above terms in the utility model can be understood according to the specific circumstances.

[0025] As Figures 1-2 shown, the embodiment provides a SNCR subarea system suitable for deep peak shaving and transformation of a circulating fluidized bed boiler, which comprises two boilers, two separators (traditional gas-solid separators, such as a cyclone separator or a bag-type dust collector, and Figure 1 the E frame selected area in the utility model is a valve for subarea control of the four separators);

[0026] Each separator is installed with 40 spray guns 1, forming an independent spray area, which acts on the high ammonia water consumption and large nitrogen oxide fluctuation of the denitration system, compared with the traditional 24 spray guns 1 of each boiler, to realize ultra-low emission of nitrogen oxides, and the model of the spray gun 1 is HNCERIJX-122 three-interface spray gun 1 (also can use traditional 316L three-interface spray gun 1), the three interfaces of the spray gun 1 are connected with the reducing agent (I pipeline), the atomizing air (H pipeline) and the cooling wind branch pipeline (G pipeline) through the bendable connecting pipe, which has the characteristics of better atomization effect, longer spraying distance, and can adapt to high temperature, high dust, high flow rate and strong wear environment, the spray guns 1 at each separator are uniformly controlled by the flow regulating valve, and the spray guns 1 are also independently controlled by the valve and measured by the installed metal rotor flowmeter;

[0027] It should be noted that the spray gun 1 is part of the spray assembly in the traditional boiler SNCR system, which is used to realize the reducing agent spraying function, in addition to the spray gun 1, the spray assembly also includes an air atomizing sprayer, a connecting piece for connecting to the boiler support and a quick connector, and a long steel wire woven bendable flexible hose for connecting the reducing agent pipeline, the atomizing air pipeline and the cooling wind pipeline with the spray gun 1;

[0028] In detail, the position of the spray gun 1 is determined by numerical simulation calculation of the flue gas flow and NOx concentration in the separator inlet flue, a three-dimensional geometric model of the boiler and its flue can be established by CAE, the geometric model is divided into grid units suitable for calculation, and then the CFD software (such as ANSYS Fluent, OpenFOAM, etc.) is used to simulate the flow of flue gas in the flue, the NOx generation and reduction reaction mechanism is added in the CFD model, the influence of chemical reaction on the flow field and temperature field is considered, then the arrangement of the spray gun 1 is tested at different positions to simulate the influence of the injection of reducing agent (such as ammonia water or urea) on the NOx concentration, the change of the flue gas flow field and the NOx concentration field is determined by analyzing the simulation results, and the effective area of the reaction is identified. The above process belongs to the traditional simulation calculation method;

[0029] The spray gun 1 is provided with three inlets, which are marked as J, K and L in Figure 3 respectively for conveying ammonia water solution, atomizing purge air and jacket cooling air (respectively connected with Figure 2The G, H, and I pipes in the nozzle are corresponding and connected. The spray gun 1 consists of a solution pipe, a nozzle, an atomizing air pipe, a cooling air pipe, and a support structure. The solution pipe is used to mix the reducing agent (such as ammonia solution) with the atomizing purge air to form fine droplets. This atomization helps the reducing agent to be fully dispersed in the flue gas and improves its reaction efficiency with nitrogen oxides. The nozzle consists of a liquid cap, an external threaded connector, an air cap, and a nozzle. The air cap is made of Hastelloy, which is corrosion-resistant, wear-resistant, and high-temperature resistant. The nozzle body (including the liquid cap and external threaded connector) is made of 316L stainless steel.

[0030] Both boilers are equipped with separate conveying systems for conveying ammonia solution and dilution water, which are used to supply the spray gun 1 at the same boiler. Specifically, the system includes two ammonia solution conveying pumps and two dilution water pumps, and is equipped with necessary structural components such as ammonia solution and dilution water pipelines, static mixers, valves and flow measurement elements.

[0031] Compared to the traditional design where two boilers share a single ammonia solution and dilution water supply pipeline, meaning that the two boilers can only receive the same amount of ammonia and dilution water at the same time and cannot be adjusted individually according to their respective needs, and when the operating load and combustion conditions of the two boilers are significantly different, a uniform supply of denitrifying agent may cause the nitrogen oxide (NOx) emissions of one boiler to fail to meet the requirements, by configuring an independent supply system and control equipment for each boiler, the supply of denitrifying agent can be flexibly adjusted according to their respective load and combustion conditions, thereby achieving more precise nitrogen oxide emission control;

[0032] Each boiler is equipped with a separate ammonia storage tank connected to the conveying system, ensuring that the ammonia storage capacity meets the unit's operating requirements even when the ultra-low NOx emission limit is reduced and more ammonia is needed for the reaction.

[0033] It should be noted that, based on the layout of the conveying system, the four separators and the furnace section are controlled in zones. Parameters such as combustion temperature allow for individual adjustment of the upper and lower reaction sections of the separator and furnace denitrification processes. Zone control is achieved when the operating parameters of the upper and lower reaction sections are met. It should be noted that the upper and lower sections refer to the separator and the furnace; whichever section's parameters meet the ammonia-water reaction conditions can be adjusted in a zone, saving denitrification agent and providing greater flexibility. Simultaneously, the four separators and the left and right furnace sections are controlled in zones via the conveying system and valves (e.g., Figure 1 The area within the F-frame is the zone control valve for the furnace and separator. Simultaneously, based on changes in coal quality, combustion degree, and extreme conditions during operation, the left and right sides of the boiler furnace are controlled separately, allowing for targeted adjustment of the denitrification system, thereby achieving economical, effective, and stable reduction of NOx emissions.

[0034] Meanwhile, automatic control is implemented for the equipment at each boiler (such as various pumps and valves, which can be automatically controlled, and will not be elaborated here). The controller model is EDPFNT-DPUVB, and the control system is the Guoneng Zhishen DCS control system. The purpose is to automatically adjust the nitrogen oxides of a single boiler.

[0035] The working principle is as follows: The denitrification delivery system introduces the denitrification agent (20% concentration ammonia water) stored in the ammonia water tank into the ammonia water pressure stabilizing tank through an ammonia water booster pump. The ammonia water and dilution water are combined with the static mixer after passing through their respective pump outlets and valves. By adjusting the pump output, the ammonia water flow rate and the dilution water flow rate are mixed at a ratio of 1:3. The ammonia water concentration after mixing in the static mixer is approximately 5%. After mixing, it is introduced into the ammonia water inlet of each spray gun 1 through the ammonia water delivery pipeline. The ammonia water flows to the nozzle and mixes with the compressed air in the jacket of the spray gun 1 to form an atomization for spraying. The spray gun 1 has a jacket structure with a total of three inlets: compressed air, cooling air, and denitrification agent, and one outlet and nozzle. The denitrification agent and compressed air are combined at the nozzle to form an atomization for spraying. It combines with the flue gas generated during combustion to produce ammonia gas, which reacts with nitrogen oxides, thereby reducing the formation of nitrogen oxides. The cooling air mainly removes the heat generated during boiler combustion, thereby protecting the spray gun 1 and nozzle from high-temperature burn-out.

[0036] The system consists of four separators ( Figure 1 The four separators (represented by A, B, C, and D respectively) are arranged in the dense phase zone of the furnace. Each separator has ten spray guns, six spray guns on the front and rear walls of the dense phase zone of the furnace, and two spray guns on the left and right walls, for a total of 56 spray guns. The generation of nitrogen oxides is mainly affected by the boiler bed temperature and the boiler oxygen content. The separators or furnace can be operated separately according to the boiler combustion conditions (boiler load, temperature range) to suppress the generation of nitrogen oxides more efficiently and energy-savingly.

[0037] It should be noted that the structure of this utility model can be implemented in many different forms and is not limited to the embodiments. Any equivalent transformations made by those skilled in the art based on the content of this utility model specification and drawings, or direct or indirect applications in other related technical fields, such as the loading and unloading of other items, are included within the protection scope of this utility model.

Claims

1. A SNCR zoned system suitable for deep peak-shaving retrofit of a circulating fluidized bed boiler, characterized in that: Two boilers are included, and two separators are installed in the two boilers respectively; Forty spray guns are installed in each separator to form an independent spraying area, and flow regulating valves, valves and metal rotor flow meters are installed in the spray guns in each separator; Two boilers are provided with separate conveying systems for conveying ammonia water solution and dilution water respectively; Each boiler is provided with a separate ammonia water storage tank.

2. The SNCR zoned system suitable for deep peak-shaving retrofit of a circulating fluidized bed boiler of claim 1, wherein: The positions of the spray guns are determined by numerical simulation calculation of the flue gas flow and NOX concentration at the inlet of the separator.

3. The SNCR zoned system suitable for deep peak-shaving retrofit of a circulating fluidized bed boiler of claim 1, wherein: The spray guns are provided with three inlets for conveying ammonia water solution, atomizing blowing air and jacket cooling air respectively.

4. The SNCR zoned system suitable for deep peak-shaving retrofit of a circulating fluidized bed boiler of claim 1, wherein: The spray gun is composed of a solution pipe, a nozzle, an atomizing air pipe, a cooling air pipe and a support structure, and the nozzle is composed of a liquid cap, an external threaded joint, an air cap and a spray opening.

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