阅读说明：本技术 一种直吹式制粉系统磨煤机出口温度的控制方法及系统 (Control method and system for outlet temperature of coal mill of direct-fired pulverizing system ) 是由 赵晴川 田春晓 张绪辉 赵中华 刘景龙 崔福兴 于 2021-07-02 设计创作，主要内容包括：本公开提供了一种直吹式制粉系统磨煤机出口温度的控制方法及系统,包括：获取SCR脱硝系统入口的氮氧化物含量；基于炉煤的可燃基挥发分与SCR脱硝系统入口的氮氧化物含量关系建立估计模型,将氮氧化物量输入估计模型确定可燃基挥发分估值；根据可燃基挥发分估值生成磨煤机出口温度控制策略,根据控制策略调整磨煤机出口温度；能够实时判断入炉煤质的挥发分,运行中可以根据煤质挥发分水平,在线调整磨煤机出口温度至最佳值运行,保证锅炉经济性达到最佳。(The utility model provides a control method and system for the outlet temperature of a coal mill of a direct-fired pulverizing system, which comprises the following steps: acquiring the content of nitrogen oxides at an inlet of an SCR denitration system; establishing an estimation model based on the relationship between the combustible base volatile matter of the furnace coal and the content of nitrogen oxide at the inlet of the SCR denitration system, and inputting the quantity of the nitrogen oxide into the estimation model to determine an estimated value of the combustible base volatile matter; generating a coal mill outlet temperature control strategy according to the estimated value of the combustible base volatile component, and adjusting the coal mill outlet temperature according to the control strategy; the volatile component of the coal entering the boiler can be judged in real time, the outlet temperature of the coal mill can be adjusted to the optimal value on line to operate according to the volatile component level of the coal during operation, and the economical efficiency of the boiler can be guaranteed to be optimal.)

1. A control method for the outlet temperature of a coal mill of a direct-fired pulverizing system is characterized by comprising the following steps:

acquiring the content of nitrogen oxides at an inlet of an SCR denitration system;

establishing an estimation model based on the relationship between the combustible base volatile matter of the furnace coal and the content of nitrogen oxide at the inlet of the SCR denitration system, and inputting the quantity of the nitrogen oxide into the estimation model to determine an estimated value of the combustible base volatile matter;

and generating a coal mill outlet temperature control strategy according to the estimated value of the combustible base volatile component, and adjusting the coal mill outlet temperature according to the control strategy.

2. The method of claim 1, wherein the step of modeling the estimate comprises:

acquiring combustible base volatile components of a coal sample at an inlet of a coal mill under a set boiler load and the content of nitrogen oxides at an SCR denitration inlet of the boiler;

adjusting the load of the boiler, repeating the steps for a set number of times to output a detection result, and analyzing and processing the detection result to obtain a relation curve graph of combustible-based volatile matter of the coal as fired of the boiler and nitrogen oxide content at the inlet of the SCR denitration system;

and establishing an estimation model according to the content relation curve graph.

3. The method of claim 2, wherein the boiler SCR denitration inlet nitrogen oxide content is matched to the time of capture of combustible-based volatiles of the coal sample at the coal pulverizer inlet.

4. The method of claim 2, wherein the test results are all test results for different boiler loads.

5. The method of claim 1 further comprising obtaining a combustible-based volatile matter content of a coal sample at an inlet of the coal pulverizer and a nitrogen oxide content at an SCR denitration inlet of the boiler at a set boiler load.

6. The method of claim 1 wherein generating a mill outlet temperature control strategy based on the estimated combustible based volatiles, and wherein adjusting the mill outlet temperature based on the control strategy comprises determining a maximum safe limit for the mill outlet temperature for different volatiles of the coal entering the furnace to form the mill outlet temperature control strategy.

7. The method of claim 1, wherein the nitrogen oxides are NOx and the combustible based volatile matter Vdaf of the coal as fired is obtained by an industrial analysis method after sampling the coal as fired.

8. The method of claim 1, wherein said adjusting according to a coal mill outlet temperature control strategy comprises controlling a coal mill outlet temperature by adjusting an inlet temperature control valve to control a temperature of a coal mill inlet air stream.

9. The method of claim 1, wherein the step of obtaining the amount of nitrogen oxides at the inlet of the SCR denitration system comprises obtaining the amount of nitrogen oxides at the inlet of the SCR denitration system by disposing a nitrogen oxide detecting element at the inlet of the SCR denitration system.

10. The utility model provides a control system of direct-fired formula powder process system coal pulverizer outlet temperature which characterized in that includes:

the detection module is used for acquiring the nitrogen oxide amount at the inlet of the SCR denitration system;

the data processing module is used for establishing an estimation model based on the relationship between the combustible-base volatile matter of the furnace coal and the content of nitrogen oxide at the inlet of the SCR denitration system, and inputting the quantity of the nitrogen oxide into the estimation model to determine an estimated value of the combustible-base volatile matter;

and the control module is used for generating a coal mill outlet temperature control strategy according to the estimated value of the combustible base volatile component and adjusting the coal mill outlet temperature according to the control strategy.

Technical Field

The disclosure relates to a method and a system for controlling the outlet temperature of a coal mill of a direct-fired pulverizing system.

Background

The statements in this section merely provide background information related to the present disclosure and may not necessarily constitute prior art.

The outlet temperature of the coal mill is closely related to the operation safety of the coal pulverizing system and the operation economy of the boiler. The boiler efficiency can be improved by improving the outlet temperature of the coal mill, the coal consumption of the coal-fired thermal generator set is reduced, and the economic benefit is considerable. However, the upper limit value of the outlet temperature of the coal mill is limited by the danger of spontaneous combustion and deflagration of coal powder in a coal pulverizing system, the higher the volatile content of the coal is, the higher the tendency of spontaneous combustion and deflagration is, and the lower the outlet temperature of the coal mill to be controlled is. The outlet temperature of the coal mill is increased, the safety margin of the operation of a pulverizing system is necessarily reduced, and the risk of spontaneous combustion and deflagration of the coal mill is increased. DL/T466-2017, namely the regulations of the type selection guide rule of the coal mills in power stations and the coal pulverizing systems, and the upper limit of the outlet temperature of the coal mills of the various types of coal pulverizing systems is determined according to the difference of the volatile component contents of different coal types. To ensure the operational safety of the pulverizing system, the mill outlet temperature specified by this standard tends to be a conservative lower fixed value. Especially in recent years, due to the fact that the coal-fired unit is subjected to deep peak regulation and frequent start-stop peak regulation, a powder preparation system is frequently operated at start-stop and low-load operation, and factors such as powder accumulation spontaneous combustion and coal powder concentration change cause the increase of spontaneous combustion and even detonation risks; in addition, the coal market fluctuation, the coal source supply shortage, the boiler coal quality mixing, the high volatile component coal blending frequently occur the spontaneous combustion of the coal pulverizing system and even the deflagration phenomenon, and bring the serious threat to the safe and economic operation of the enterprise, therefore, the outlet temperature control of the coal mill in the actual operation tends to a lower limit value. From the current testing and practice of power plants, there is much room for improvement in coal mill outlet temperatures. According to the test, the coal consumption of power supply is reduced by 1-2 g/kwh when the outlet temperature of the coal mill is increased by 10 ℃, and the economic benefit is very obvious. The key point is that the unit can quickly judge the volatile component level of coal as fired in real time during operation, adjust the outlet temperature of the coal mill in time, keep the higher outlet temperature of the coal mill to operate as much as possible and realize higher economical operation; when high-volatile coal quality is burned, the outlet temperature of the coal mill is timely reduced to operate, and spontaneous combustion and deflagration accidents of the coal mill are avoided, so that the boiler can burn coal with a wider range of volatile components, and the safety of peak regulation and the flexibility of fuel are improved.

Generally, the volatile components of the coal as fired are obtained by an industrial analysis method, and the steps of sampling, sample preparation, chemical analysis and the like of the coal are required, so that the time of several hours is consumed, and the volatile components cannot be used as a basis for judging the change of the coal quality in time in the operation process of the coal mill. Therefore, in the actual operation process of the thermal power plant, operators cannot know the volatile content condition of the burning coal as fired, and have to operate conservatively to control the outlet temperature of the coal mill at a lower level so as to avoid spontaneous combustion and deflagration accidents of a coal pulverizing system; and the outlet temperature of the coal mill is kept at a fixed value, and the real-time online adjustment cannot be carried out according to the change condition of the coal quality, so that the running economy of the unit is influenced.

Disclosure of Invention

In order to solve the problems, the disclosure provides a method and a system for controlling the outlet temperature of a coal mill of a direct-fired pulverizing system.

In a first aspect, the present disclosure provides a method for controlling an outlet temperature of a coal mill of a direct-fired pulverizing system, including:

acquiring the content of nitrogen oxides at an inlet of an SCR denitration system;

establishing an estimation model based on the relationship between the combustible base volatile matter of the furnace coal and the content of nitrogen oxide at the inlet of the SCR denitration system, and inputting the quantity of the nitrogen oxide into the estimation model to determine an estimated value of the combustible base volatile matter;

and generating a coal mill outlet temperature control strategy according to the estimated value of the combustible base volatile component, and adjusting the coal mill outlet temperature according to the control strategy.

In a second aspect, the present disclosure provides a control system for outlet temperature of a coal mill of a direct-fired pulverizing system, comprising:

the detection module is used for acquiring the nitrogen oxide amount at the inlet of the SCR denitration system;

the data processing module is used for establishing an estimation model based on the relationship between the combustible-base volatile matter of the furnace coal and the content of nitrogen oxide at the inlet of the SCR denitration system, and inputting the quantity of the nitrogen oxide into the estimation model to determine an estimated value of the combustible-base volatile matter;

and the control module is used for generating a coal mill outlet temperature control strategy according to the estimated value of the combustible base volatile component and adjusting the coal mill outlet temperature according to the control strategy.

Compared with the prior art, this disclosure possesses following beneficial effect:

1. the method comprises the steps of establishing an estimation model based on the relationship between combustible base volatile components of furnace coal and nitrogen oxide content at an inlet of an SCR denitration system, and inputting the nitrogen oxide amount into the estimation model to determine an estimated value of the combustible base volatile components; and generating a coal mill outlet temperature control strategy according to the estimated value of the combustible base volatile component, and adjusting the coal mill outlet temperature according to the control strategy. The method overcomes the defects of long period and non-real time inherent in the traditional method for obtaining the volatile components of the coal as fired by industrial analysis, enables operators to obtain the volatile components of the coal as fired in real time, avoids the conservative operation mode of low outlet temperature control of the coal mill in the past, and improves the operation economy of the boiler.

2. This is disclosed adopts and to generate coal pulverizer outlet temperature control strategy according to combustible base volatile component valuation, adjusts coal pulverizer outlet temperature according to control strategy, and as the coal as fired volatile component produces the fluctuation, the operation personnel can discover immediately to in time reduce coal pulverizer outlet temperature and move to safe range, guarantee not to take place powder process system spontaneous combustion, detonation accident. Therefore, the boiler can improve the safety of a pulverizing system during deep peak shaving operation, can burn coal with wider range of volatile components, and improves the flexibility of fuel.

Drawings

The accompanying drawings, which are incorporated in and constitute a part of this application, illustrate embodiments of the application and, together with the description, serve to explain the application and are not intended to limit the application.

FIG. 1 is a flow chart of a method for controlling the outlet temperature of a coal mill of a direct-fired pulverizing system according to the present disclosure;

fig. 2 is a schematic structural diagram of a control system for the outlet temperature of a coal mill of the direct-fired pulverizing system according to the present disclosure.

FIG. 3 is a graph of the relationship between combustible-based volatile matter Vdaf of coal as fired and inlet NOx of SCR denitration system obtained by the boiler test in example 1;

wherein, 1, the inlet air flow of the coal mill; 2. a coal mill inlet temperature control valve; 3. a coal mill; 4. Raw coal; 5. mixing coal powder and air; 6. a hearth; 7. a stream of combustion flue gases; 8. an SCR denitration system inlet NOx measuring element; 9. an SCR denitration system; 10. the NOx measurement is fed back to the control valve signal.

The specific implementation mode is as follows:

the present disclosure is further described with reference to the following drawings and examples.

It should be noted that the following detailed description is exemplary and is intended to provide further explanation of the disclosure. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.

It is noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments according to the present application. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, and it should be understood that when the terms "comprises" and/or "comprising" are used in this specification, they specify the presence of stated features, steps, operations, devices, components, and/or combinations thereof, unless the context clearly indicates otherwise.

Interpretation of terms: the combustible-based volatile matter is a volatile matter calculated based on the combustible matter after the removal of the ash.

The volatile components of coal are mainly combustible gases such as carbon monoxide, hydrogen sulfide and certain hydrocarbons except a small amount of non-combustible gases such as oxygen, carbon dioxide, nitrogen and the like. Therefore, the volatile matter easily ignites. After the volatile matter is ignited, the non-volatile part of the coal can be heated intensely, so that the coal can be promoted to be ignited and burnt rapidly. Therefore, the ignition temperature of high volatile coal dust is low, around 800 ℃, while the ignition temperature of low volatile coal dust is high, possibly up to 1100 ℃. The volatile matter has great influence on the ignition temperature of the pulverized coal and the complete combustion of the fuel, so the content of the volatile matter is an important characteristic influencing the combustion of the fuel. The design of a combustor, the selection of the fineness of the pulverized coal, the determination of the primary air rate, the explosion prevention of a pulverizing system and the like are all closely related.

Example 1

As shown in figure 1 of the drawings, in which,

a control method for the outlet temperature of a coal mill of a direct-fired pulverizing system comprises the following steps:

acquiring the content of nitrogen oxides at an inlet of an SCR denitration system;

establishing a combustible base volatile component estimation model based on the content relation of combustible base volatile components and nitrogen oxides of the furnace coal, and determining an estimated value of the combustible base volatile components through the nitrogen oxide-based combustible base volatile component estimation model;

and generating a coal mill outlet temperature control strategy according to the estimated value of the combustible base volatile component, adjusting the coal mill outlet temperature according to the control strategy, and adjusting the coal mill outlet temperature according to the coal mill outlet temperature control strategy.

As a specific embodiment, the step of obtaining the nitrogen oxide amount at the inlet of the SCR denitration system includes obtaining the nitrogen oxide amount at the inlet of the SCR denitration system by arranging a nitrogen oxide detection element at the inlet of the SCR denitration system. The nitrogen oxide detection element may be a nitrogen oxide detector.

In another embodiment, the step of establishing an estimation model includes,

acquiring combustible base volatile components of a coal sample at an inlet of a coal mill under a set boiler load, and detecting the content of nitrogen oxides at an SCR denitration inlet of the boiler matched with the combustible base volatile components in time;

and adjusting the boiler load, repeating the steps for a set number of times, outputting all detection results under different boiler loads, and analyzing and processing the detection results to obtain a relation curve graph of combustible-based volatile matter of the coal as fired of the boiler and nitrogen oxide content at the inlet of the SCR denitration system. The data of the national 39 direct-fired pulverizing systems tested by western's safety thermal institute show that the volatile components of the coal as fired and the NOx at the inlet of the SCR denitration system are all in negative correlation function relationship, that is, the generation amount of NOx is reduced along with the increase of the volatile components. The principle is as follows: the low NOx combustion technology in the boiler which is most widely applied at present adopts air staged combustion, so that the oxygen amount at the initial stage of pulverized coal combustion is pertinently reduced, and the generation of NOx is effectively reduced by inhibiting the combustion rate of a main combustion zone and reducing the temperature. The more volatile the coal, the more combustible is precipitated in the initial stage of combustion, and the more easily the pulverized coal is ignited, so the more oxygen is required. Under the condition of a certain primary air rate, an oxygen-deficient atmosphere is formed in the initial stage of combustion, so that the generation of NOx can be effectively reduced. Therefore, the higher the volatile content of the coal, the lower the NOx generated by air staged combustion, which shows that the relationship between the volatile content of the coal as fired and the NOx at the inlet of the SCR denitration system is a negative correlation function.

Specifically, through a test method, such as the test data of a 350MW boiler shown in fig. 2, a coal sample is taken at the inlet of a coal mill under different loads of the boiler, and through industrial analysis, the combustible base volatile component Vdaf of the coal as fired is obtained. And simultaneously recording a NOx measured value at an SCR denitration inlet of the boiler to obtain a relation curve chart of combustible base volatile components Vdaf of coal as fired of the boiler and the NOx at the inlet of the SCR denitration system. Specifically, combustible base volatile component Vdaf of the coal as fired is obtained by an industrial analysis method after sampling the coal as fired, and a NOx measured value at an SCR denitration inlet is obtained by measuring through an NOx online instrument arranged at an SCR denitration inlet of the boiler. The industrial analysis method is a general term for measuring four analysis item indexes including moisture (M), ash (a), volatile matter (V) and fixed carbon (Fc) of coal. The industrial analysis of coal is a main index for understanding the characteristics of coal quality and is also a basic basis for evaluating the coal quality. Usually, the moisture, ash and volatile components of coal are directly measured, and the fixed carbon is calculated by the subtraction method. The industrial analysis method is characterized in that the industrial analysis of coal is laboratory analysis, a certain amount of general analysis test coal sample is weighed by adopting the standard GB/T2122008 coal industrial analysis method, the general analysis test coal sample is placed in a porcelain crucible with a cover, and the porcelain crucible is isolated from air and heated for 7 min at the temperature of 900 +/-10 ℃, so that the reduced mass accounts for the fraction of the mass of the coal sample, and the moisture content of the coal sample is subtracted to be used as the volatile component of the coal sample.

Generating a coal mill outlet temperature control strategy according to the estimated combustible base volatile component value, and adjusting the coal mill outlet temperature according to the control strategy comprises determining the highest safety limit value of the coal mill outlet temperature when different coal fired volatile components are tested and searched through a boiler test, so as to form the coal mill outlet temperature control strategy. Under the strategy, the outlet temperature of the coal mill is improved as much as possible, the highest operation economy of the boiler can be achieved, and spontaneous combustion and deflagration of a pulverizing system are avoided. As shown in fig. 1, the highest economy can be ensured, and spontaneous combustion and deflagration of the pulverizing system can be avoided. The maximum safety limit value of the outlet temperature of the coal mill is obtained by a test method, and the specification of the maximum allowable temperature of the outlet of the coal mill in the power station coal mill and pulverizing system model selection guide rule of L/T466-2017 can be consulted by a label. The standard specified value is only conservative, and there is room for improvement based on experimental investigation.

In one embodiment, the range of the outlet temperature of the coal mill to be controlled is determined according to the range of the estimated value of the combustible-based volatile component, and the temperature control strategy is as follows: estimating that the volatile component is more than 24%, indicating that the coal belongs to the explosive coal, and strictly controlling the outlet temperature of the coal mill to be less than 100 ℃; estimating that the volatile component is 18-24%, indicating that the coal has a medium deflagration tendency, and controlling the outlet temperature of the coal mill at 110 ℃ below zero; the volatile content of the combustible base is less than 18 percent, which indicates that the coal belongs to the range of coal which is not easy to deflagrate, and the outlet temperature of the coal mill can be controllably increased to <130 ℃.

The nitrogen oxide is NOx, the combustible base volatile component Vdaf of the coal as fired is obtained by an industrial analysis method after sampling the coal as fired, and a NOx measured value at an SCR denitration inlet is obtained by measuring through an NOx online instrument arranged at an SCR denitration inlet of the boiler.

As one embodiment, adjusting the coal mill outlet temperature according to the coal mill outlet temperature control strategy includes controlling a temperature of the coal mill inlet air flow according to the coal mill outlet temperature control strategy to thereby control the coal mill outlet temperature. As another embodiment, the temperature of the coal mill inlet air stream is controlled by adjusting an inlet temperature control valve to control the coal mill outlet temperature.

Specifically, in the normal operation process of the boiler, the estimated volatile component Vdaf of the coal as fired is obtained according to the obtained relation curve of the coal Vdaf and the inlet NOx of the SCR denitration system through the display value of the NOx monitoring instrument at the SCR denitration inlet, and then the outlet temperature of the coal mill is adjusted according to the outlet temperature control strategy of the coal mill.

Example 2

A control system for outlet temperature of a coal mill of a direct-fired pulverizing system comprises:

the detection module is used for acquiring the nitrogen oxide amount at the inlet of the SCR denitration system;

the data processing module is used for establishing an estimation model based on the relationship between the combustible-base volatile matter of the furnace coal and the content of nitrogen oxide at the inlet of the SCR denitration system, and inputting the quantity of the nitrogen oxide into the estimation model to determine an estimated value of the combustible-base volatile matter;

and the control module is used for generating a coal mill outlet temperature control strategy according to the estimated value of the combustible base volatile component and adjusting the coal mill outlet temperature according to the control strategy.

Specifically, the detection module, the data processing module and the control module are set by the control method of the outlet temperature of the coal mill of the direct-fired pulverizing system according to the embodiment.

In the normal operation process of the boiler, as shown in fig. 1, coal 4 is ground into coal powder by a coal mill 3, air carries coal powder airflow 5 to enter a hearth 6 for combustion, the generated flue gas flow 7 reaches an inlet of an SCR denitration system 9, the concentration of NOx in the flue gas is immediately measured by a measuring element 8, a feedback signal 10 is sent to an inlet air temperature control system 2 of the coal mill, and the temperature of an inlet air flow 1 of the coal mill is controlled according to an outlet temperature control strategy of the coal mill, so that the purpose of controlling the outlet temperature of the coal mill is achieved.

Although the present disclosure has been described with reference to specific embodiments, it should be understood that the scope of the present disclosure is not limited thereto, and those skilled in the art will appreciate that various modifications and changes can be made without departing from the spirit and scope of the present disclosure.