Boiler Combustion Control System Using Pulverized Coal Heat Measurement System

Abstract

This patent discloses a boiler combustion control system using a pulverized coal heat measurement system. The pulverized coal heat measurement system includes: a coal calorific value measuring instrument, a coal feeder, and a data acquisition controller. The coal calorific value measuring instrument measures the calorific value Q of the raw coal. 原P , the coal feeder measures the raw coal weight W 原P , and according to Q 原P and W 原P Calculate the output heat M of coal powder from the coal mill 粉P、 W 粉P And calorific value of coal powder Q 粉P , the data acquisition controller receives Q 粉P , W 粉P and M 粉P , calculate the weight, calorific value and heat of the coal powder entering the furnace. The boiler combustion control system receives the coal powder weight, calorific value and heat signals measured by the coal powder heat measurement system entering the furnace, and controls the boiler combustion system based on these signals.

Description

Technical Field

[0001] The invention relates to online measurement and control of coal calorific value, and in particular to measurement of calorific value of coal powder fed into a coal-fired boiler and combustion control of the boiler. Background Art

[0002] The pulverized coal boiler in power plants generally adopts 3-6 layers of pulverized coal making and supply systems. Each layer uses a coal mill with four air delivery pipes to supply pulverized coal to the burner, and four air distribution pipes to supply air to the burner. The four burners use the four-corner injection technology to spray air and pulverized coal into the furnace. The equipment on each layer is the same. Take the first layer as an example. Figure 1 As shown. The weight of coal powder entering the furnace, the calorific value of coal powder and the air supply volume are important parameters for boiler combustion control, which directly affect the working conditions and combustion quality of coal powder combustion in the furnace. For many years, the weight detection and calorific value detection of air-delivered coal powder have always attracted the attention of relevant technical personnel at home and abroad. The balance method, energy method, photoelectric detection method, capacitance method, capacitance tomography method, laser method, microwave method, electrostatic induction method, etc. have been adopted successively to carry out the research and development of the weight and calorific value of coal powder in air-delivered pipelines. However, due to the measurement difficulties of air-powder two-phase flow detection and high temperature, high pressure, high speed, high friction of coal powder in pipelines, small weight load, and variable motion trajectory, most of them are currently in the research and development stage and have not yet been applied in production.

[0003] Since there is no means to detect the weight and calorific value of the pulverized coal delivered by air, the heat parameters of the pulverized coal entering the furnace cannot be given. Therefore, the existing pulverized coal combustion control in boilers can only adopt an indirect method, that is, to construct a so-called fuel quantity heat signal M that can reflect the amount of fuel entering the furnace and the change in the calorific value of the fuel, and use M to build a combustion control system. The M signal is obtained by the following method:

[0004] 1. The weight of raw coal measured by the coal feeder at each layer (W 原煤A ......W 原煤F ) is used as the basis, and after time dynamic correction, it is determined to be the coal powder weight output by each layer of coal mill (W 粉A ......W 粉F ), and then sum the weight of each layer of coal powder to get: W C =W 粉A +…W 粉F , the W C It is the total weight of coal powder entering the furnace.

[0005] 2. In the drum chamber heat exchange, the heat signal D is constructed according to the energy obtained by the steam medium Q , Where D-steam flow, C b -Energy storage coefficient, P-saturated steam pressure. Heat signal D Q Total absorbed heat Q r Proportional, Q rIt is proportional to the heat of the coal powder entering the furnace (weight of coal powder × calorific value), so D Q It is also proportional to the heat of the coal powder. Therefore, D Q It can be used to characterize the change of the amount of pulverized coal entering the furnace and the calorific value. C Under certain conditions, D Q Used to characterize the fuel calorific value Q 粉 According to M C , D Q The measurement method of fuel quantity heat signal M is as follows: Figure 2 shown.

[0006] The combustion control system adjusts the fuel quantity of 24 powder delivery pipelines according to M, such as Figure 3 shown.

[0007] The control system adjusts the air flow of the 24 air distribution ducts according to M, such as Figure 4 shown.

[0008] from Figure 2 , Figure 3 , Figure 4 It is not difficult to see that the main problems of the existing combustion control system based on M are:

[0009] 1. There are many links and factors that affect the construction of the fuel quantity heat signal M, and the M value varies greatly. There is a large error between it and the actual heat of the coal powder entering the furnace;

[0010] 2. Using heat signal D Q The calorific value correction of the pulverized coal entering the furnace is a delayed correction, that is, using D Q Corrected: At this time, the heat of the pulverized coal is not to generate D Q In addition, the influence of D Q The changing factors also affect D Q Correction of calorific value;

[0011] 3. Since M is highly volatile and inaccurate, adjusting and controlling the fuel quantity and air distribution volume of the 24 pipelines based on M will cause large disturbances and errors; it will also cause large deviations in coal powder weight between the 24 powder delivery pipelines and large deviations in air distribution volume between the 24 air distribution pipelines.

[0012] Aiming at the problems existing in the existing boiler combustion control system, a "boiler combustion control system using a pulverized coal heat measurement system" is proposed. Summary of the invention

[0013] This patent is based on the analysis of the working characteristics of coal mills and boilers. Under specific conditions, it determines the functional relationship between the raw coal entering the coal mill and the coal powder output, namely, W 粉P =f(W 原P, t), M 粉P =f(M 原P , t), and find the mathematical model of the functional relationship to achieve online measurement of the weight, calorific value, and heat of the coal powder entering the furnace. In short, by measuring the raw coal W 原P , Q 原P , calculate the weight, calorific value and heat of the coal powder entering and leaving the furnace, which avoids the measurement of two-phase flow of wind-conveyed coal powder and the measurement difficulties of high pressure, high temperature, high speed, high friction, small load and changeable trajectory of wind-conveyed coal powder.

[0014] A "boiler combustion control system using a pulverized coal heat measurement system" consists of two parts:

[0015] 1) Heat measurement system of coal powder entering the furnace;

[0016] 2) Boiler combustion control system;

[0017] The calorimetric measurement system for coal powder entering the furnace is characterized by:

[0018] a) A coal calorific value measuring instrument is installed at the feed pipe (2) between the raw coal bunker (1) and the coal feeder (3) of each layer of the pulverizing and supplying system of the boiler to measure the calorific value Q of the raw coal entering the coal feeder of each layer. 原P P represents the number of layers, P = A, B, C, D, E, F;

[0019] b) Coal feeders (3) at each layer, used to measure the weight W of raw coal entering the coal mill at each layer 原P ; The coal calorific value measuring instrument of each layer measures the calorific value signal Q of the raw coal according to the measured value 原P And receive the raw coal weight signal W measured by the coal feeder on this layer 原P , the heat M of coal powder output from each coal mill can be calculated 粉P , coal powder weight W 粉P , calorific value of pulverized coal Q 粉P , which is expressed as follows:

[0020]

[0021]

[0022]

[0023] In the formula, Δt-collection time; t1-coal mill pulverizing time; t2-coal powder output time or coal powder adjustment time.

[0024] c) The data acquisition controller receives the coal mill output signal M measured by the coal calorific value measuring instrument on each layer. 粉P , W 粉P , Q 粉PCalculate the total heat M of the coal powder entering and leaving the furnace 总 , total weight of coal powder W 总 And the calorific value of coal powder Q 粉炉 , which is expressed as follows:

[0025] M 总 =M 粉A +M 粉B +………M 粉F

[0026] W 总 =W 粉A +W 粉B +………W 粉F

[0027]

[0028] The boiler combustion control system is characterized in that the boiler combustion control system receives an output signal M from a data acquisition controller. 总 , M 粉A 、M 粉B ……M 粉F and Q 粉炉 Based on these signals, one or more of the following controls are performed:

[0029] a) Use M 总 Replace M and build a system with M 总 The existing boiler combustion control system; M is the coal quantity heat signal constructed by the existing boiler control system;

[0030] b) The heat M of the pulverized coal output by each layer of coal mill 粉P Based on this, the heat of the pulverized coal in the four pulverized coal delivery pipelines on this floor is regulated and controlled;

[0031] c) The heat M of the pulverized coal output by each layer of coal mill 粉P Based on this, the air volume of the four air distribution ducts on each floor is adjusted and controlled;

[0032] d) Calorific value of coal powder used in the furnace Q 粉炉 Replace the static measurement value Q of calorific value of pulverized coal in the existing boiler control system 粉静 , the Q 粉静 It is used to compare with the heat signal D Q Common calorific value of fuel Q 粉 make corrections;

[0033] e) Use the coal heat measuring instrument of each layer of the coal powder heat measurement system to measure the heat load value M of each layer. 给P and Q of this layer 原P , W 原P The heat M of the raw coal entering the coal mill in this layer 原P M原P =W 原P ×Q 原P Perform constant heat control to make M 原P With M 给P consistent, thereby making the heat of the coal powder entering the furnace M 总 With M 给 Consistent with M 给 is the given heat load value of the entire boiler.

[0034] The in-furnace coal powder heat measurement system is characterized in that the coal calorific value measuring instrument is an X-ray coal calorific value measuring instrument, or a dual-energy gamma-ray coal calorific value measuring instrument, or a laser coal calorific value measuring instrument, or a microwave coal calorific value measuring instrument.

[0035] The coal calorific value measuring instrument is characterized in that it comprises: a sampler (101) for taking out a coal sample from a feed pipe (2); a crusher (102) for crushing the coal sample; a coal calorific value measuring device (103) for measuring the calorific value of the coal sample; and a conveyor (104) for returning the coal sample to the feed pipe (2). Figure 6 . BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 Schematic diagram of powder making and supply system equipment.

[0037] 1-Raw coal bin; 2-Feeding pipe; 3-Coal feeder; 4-Primary air fan; 5-Coal pulverizer; 6-Coal fine powder separator; 7-Powder delivery main pipeline; 7A, 7B, 7C, 7D-Powder delivery branch pipeline; 8-Powder powder distributor; 9A, 9B, 9C, 9D-Burners; 10-Air distribution main pipeline; 10A, 10B, 10C, 10D-Air distribution branch pipeline; 11-Secondary air bellows; 12-Secondary air fan.

[0038] Figure 2 The coal feeder measures the weight of the raw coal and the heat signal D Q Schematic diagram of the corrected total fuel heat signal M.

[0039] Figure 3 Schematic diagram of fuel quantity adjustment control based on M.

[0040] Figure 4 Schematic diagram of air volume adjustment control based on M.

[0041] Figure 5 Schematic diagram of the transformation of the existing boiler combustion system using the pulverized coal heat measurement system.

[0042] 1-A layer coal calorific value measuring instrument; 2-A layer coal feeder; ... 11-F layer coal calorific value measuring instrument; 12-F layer coal feeder; 13-data acquisition controller; 14-existing boiler coal control system.

[0043] Figure 6 Schematic diagram of the installation of coal calorific value measuring instrument.

[0044] 101- sampler; 102- crusher; 103- coal calorific value measuring device; 104- return conveyor.

[0045] Figure 7 Schematic diagram of constant heat control of raw coal entering the coal mill.

[0046] Figure 8 M 总 Based on this, a schematic diagram of the implementation plan of the existing boiler combustion control system is provided. DETAILED DESCRIPTION

[0047] The following is a further explanation of the patent implementation in conjunction with the accompanying drawings.

[0048] Figure 1 The present invention is a schematic diagram of the equipment composition of the pulverizing and supplying system of the first layer of an existing coal-fired boiler. The coal calorific value measuring instrument is installed at the feeding pipe (2) of the system and forms a calorific value measuring system for the pulverized coal entering the furnace with the coal feeder (3). The coal calorific value measuring instrument can directly measure the calorific value of the raw coal in the feeding pipe, or obtain a coal sample from the feeding pipe (2) for measurement. It is recommended to adopt the sampling method for measurement.

[0049] Figure 6 A schematic diagram of the installation of a coal calorific value measuring instrument at a feed pipe (2) for sampling and measuring is provided. In the figure, the sampler (101) is a screw conveyor, the crusher (102) is a high-speed rotary crusher, the calorific value measuring device (103) is an X-ray calorific value measuring device, and the return conveyor (104) is a screw conveyor. The coal calorific value measuring instrument measures the calorific value Q of the raw coal in real time. 原P At the same time, the raw coal weight signal W is received from the coal feeder (3) 原P , and according to Q 原P , W 原P Calculate the heat M of raw coal entering and leaving the coal mill 原P =Q 原P ×W 原P , so as to realize the supply of pulverized coal to the pulverizer according to the heat of raw coal. Due to the wide variety of raw coal and the large changes in coal quality parameters, the heat of the pulverized coal entering the furnace fluctuates greatly. In addition, the boiler itself has large thermal inertia and long adjustment time, which seriously affects the combustion control of the existing boiler. This transformation can be based on the given heat load M of each layer 给P The heat M of raw coal in each layer 原P Carry out heat value control to make each layer of coal entering the pulverizer 原P With each layer of M 给P be consistent.

[0050] Figure 7The heat value control schematic diagram is given. The heat of each layer of coal powder is constant, which also makes the heat of coal powder entering the furnace constant, that is, the heat of coal powder entering the furnace M 总 With a given total heat load value M 给 This modification is one of the key points in improving the existing boiler combustion control system, enabling the existing boiler combustion control system to adapt to the parameter changes of multiple coal types and coal qualities, and improving the stability of boiler operation.

[0051] Figure 8 A schematic diagram of the specific implementation scheme of "Using the pulverized coal heat measurement system to transform the existing boiler combustion control system" is given. As can be seen from the figure, the technical transformation of the present invention can be achieved by simply programming an automatic switching program in the existing boiler combustion control system:

[0052] 1) M 总 Replace M;

[0053] 2) Based on the heat M of each layer of coal powder 粉P Replace M, based on M 粉P Carry out fuel quantity regulation and control on the four powder delivery pipelines on this floor;

[0054] 3) Based on the heat M of each layer of coal powder 粉P Replace M, based on M 粉P Adjust the air volume of the four air distribution ducts on this floor;

[0055] 4) Q 粉炉 Alternative Q 粉静 Achieving Q 粉炉 With heat signal D Q Common calorific value of fuel Q 粉 correction and control.

[0056] Figure 5 A schematic diagram of the composition of "Application of pulverized coal heat measurement system to transform existing boiler combustion control system" is given, which discloses the equipment included in the pulverized coal heat measurement system, the connection between the equipment and the function of each equipment, as well as the relationship between the pulverized coal heat system and the existing boiler combustion control system.

[0057] The pulverized coal heat measurement system only provides accurate, stable, actual (not constructed) pulverized coal weight, calorific value, and heat control parameters for the existing boiler combustion control system. The existing boiler combustion control system receives these parameters to form various controls, which are not limited to the modified control given in this patent.

[0058] Compared with the boiler combustion control system before the transformation, the modified existing boiler combustion control system brings the following technical effects:

[0059] 1)M 总 More accurate and stable than M;

[0060] 2) M 总 Without the time delay of M, the time is more accurate and the time adjustment is fast;

[0061] 3) Based on the heat of each layer of coal powder (M 粉A , ...M 粉F ) is used as the basis, and the fuel quantity of the four powder delivery pipelines in this layer is adjusted and controlled more finely in layers, which can reduce heat disturbance and improve the combustion stability in the furnace. At the same time, according to the heat load M required for power generation, 给 Requirements are distributed to each layer in proportion as the given heat load value M for each layer 给P , with each layer given heat load value M 给P , constant heat control is carried out on each layer, so that the heat of the coal powder in each layer is adapted to the heat required by each layer, forming a stable temperature distribution gradient field, thereby improving the heat exchange conditions, allowing the steam to obtain more heat, and improving the thermal efficiency of the boiler.

[0062] 4) Based on the pulverized coal heat of each layer, the air is distributed to the four pipes of this layer. It is more accurate than the air distribution to 24 pipes based on M, and the air-to-pulverized coal ratio deviation is smaller, which greatly improves the uniformity and stability of pulverized coal combustion in the furnace and the pulverized coal combustion efficiency (burnout rate). In addition, it can also reduce the excess air coefficient, reduce the air distribution volume, and reduce the heat loss of exhaust gas.

[0063] 5) It can realize the forward balance calculation of the heat of the coal powder entering the furnace based on the instantaneous coal consumption of the coal powder entering the furnace. Through the positive balance calculation, the coal consumption deviation analysis of each link is carried out to find out the weak points, improve the energy management level of the power plant, and further save energy, reduce consumption and reduce emissions.

[0064] The coal powder heat measurement system of this patent is used to detect the coal powder heat M 总 , with M 总 Based on this, the boiler combustion control system for a newly built power station also falls within the protection scope of this patent.

Claims

1. A boiler combustion control system using a pulverized coal heat measurement system, which consists of two parts: 1) Heat measurement system of coal powder entering the furnace; 2) Boiler combustion control system; The calorimetric system for measuring the calorimetric value of the coal powder entering the furnace is characterized by comprising: a) A coal calorific value measuring instrument is installed at the feed pipe (2) between the raw coal bunker (1) and the coal feeder (3) of each layer of the pulverizing and supplying system of the boiler to measure the calorific value Q of the raw coal entering the coal feeder of each layer. 原P , P represents the number of layers, P = A, B, C, D, E, F; b) Coal feeders (3) at each layer, used to measure the weight W of raw coal entering the coal mill at each layer 原P ; The coal calorific value measuring instrument of each layer, according to the raw coal calorific value signal Q measured by each layer 原P And receive the raw coal weight signal W measured by the coal feeder on this layer 原P , the output heat M of coal powder from each pulverizer can be calculated 粉P , coal powder weight W 粉P , calorific value of pulverized coal Q 粉P , which is expressed as follows: In the formula, Δt-acquisition time; t 1 - coal pulverizing time; t 2 - Coal powder output time or coal powder adjustment time; c) The data acquisition controller receives the output signal M of each layer of coal mill measured by the coal calorific value measuring instrument on each layer. 粉P , W 粉P , Q 粉P And calculate the total heat M of the coal powder entering the furnace 总 , total weight of coal powder W 总 And the calorific value of coal powder Q 粉炉 , which is expressed as follows: M 总 =M 粉A +M 粉B +………M 粉F IN 总 =In 粉A +W 粉B +………In 粉F The boiler combustion control system is characterized in that the boiler combustion control system receives an output signal M from a data acquisition controller. 总 , M 粉A 、M 粉B ……M 粉F and Q 粉炉 Based on these signals, one or more of the following controls are performed: a) Use M 总 Replace M and build a system with M 总 The boiler combustion control system is based on, M is the fuel quantity heat signal constructed by the existing boiler combustion control system; b) The heat M of the pulverized coal output by each layer of coal mill 粉P Based on this, the fuel heat of the four powder delivery pipelines on this layer is adjusted and controlled at a fixed value; c) The heat M of the pulverized coal output by each layer of coal mill 粉P Based on this, the air volume of the 4 air distribution ducts on this floor is adjusted and controlled; d) Calorific value of coal powder used in the furnace Q 粉炉 The static measurement value Q of the calorific value of pulverized coal that replaces the existing pulverized coal control system 粉静 , the Q 粉静 It is used to compare with the heat signal D Q Common calorific value of fuel Q 粉 make corrections; e) Use the coal heat measuring instrument of each layer of the coal powder heat measurement system to measure the heat load value M of each layer. 给P and the Q of each layer 原P , W 原P The heat M of the raw coal entering the coal mill in this layer 原P Perform constant heat control, M 原P =W 原P ×Q 原P , so that M 原P With M 给P consistent, thereby making the heat of the coal powder entering the furnace M 总 With M 给 Consistent, M 给 is the given heat load value of the entire boiler.

2. According to the boiler combustion control system using the calorific value measurement system of the pulverized coal entering the furnace as claimed in claim 1, the calorific value measuring instrument of the coal installed at the feeding pipe (2) is: It is characterized in that The coal calorific value measuring instrument is an X-ray coal calorific value measuring instrument, or a dual-energy gamma-ray coal calorific value measuring instrument, or a laser coal calorific value measuring instrument, or a microwave coal calorific value measuring instrument.

3. The boiler combustion control system using the pulverized coal heat measurement system according to claim 1 or 2, wherein the coal calorific value measuring instrument, It is characterized in that The coal calorific value measuring instrument of each layer measures the coal calorific value Q of the layer. 原P And the raw coal weight W measured by the coal feeder on this layer 原P Calculate the heat M of the coal entering the coal mill at this layer 原P , M 原P =Q 原P ×W 原P , and then according to the given heat load value M of this layer 给P To M 原P Carry out heat value control to make the heat M of raw coal entering the coal mill 原P With M 给P consistent, thereby making the heat of the coal powder entering the furnace M 总 Constant.

4. According to the boiler combustion control system using the pulverized coal heat measurement system of claim 2, the coal calorific value measuring instrument, Its characteristics are also that It comprises: a sampler (101) for taking out coal samples from a feeding pipe (2); a crusher (102) for crushing the coal samples; a coal calorific value measuring device (103) for measuring the calorific value of the coal samples; and a conveyor (104) for returning the coal samples to the feeding pipe (2).

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