A pulverized coal boiler combustion optimization control system and method

Abstract

The present invention discloses a pulverized coal boiler combustion optimization control system and method, including a pulverized coal boiler system and a DCS control system connected to the pulverized coal boiler system and used to control the combustion adjustment of the pulverized coal boiler system; the pulverized coal boiler system includes a boiler, the pulverized coal inlet of the boiler is connected to a coal mill, and the pulverized coal outlet of the coal mill is provided with a dynamic separator; an SCR system is provided inside the boiler; both sides of the boiler are connected to an electrostatic precipitator through a flue gas exhaust pipe, wherein the electrostatic precipitator is provided with an online measuring device for the carbon content of fly ash, and the output end of the online measuring device for the carbon content of fly ash is connected to the input end of the DCS control system. The present invention can effectively reduce the carbon content of fly ash and NO x The production volume can be increased, the blending ratio of economic coal types can be improved, and huge economic benefits can be generated.

Description

Technical Field

[0001] The present invention relates to the technical field of pulverized coal boilers, and in particular to a pulverized coal boiler combustion optimization control system and method. Background Art

[0002] With the increase of installed capacity of new energy, the load fluctuation of thermal power generation units is becoming more and more frequent, and the peak-to-valley difference is getting larger and larger. At the same time, in order to reduce the power supply cost, power plants have been burning economic coal blends, so frequent combustion adjustments are required. x The direction of change in the amount of generation is often inconsistent. How to balance the carbon content of fly ash and NO x The amount generated becomes the key to combustion adjustment.

[0003] At present, the boiler air distribution method relies heavily on the experience of the operators for adjustment. Due to the different operating levels of the operators, the reserved safety margin is too large, so the economic efficiency of boiler operation needs to be improved. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a pulverized coal boiler combustion optimization control system and method, which can automatically carry out combustion optimization tests by controlling the DCS system to find the fly ash carbon content, NO x The wind distribution method with the lowest power supply cost caused by the amount of generation.

[0005] In order to solve the above technical problems, the technical solutions adopted by the present invention are as follows.

[0006] A pulverized coal boiler combustion optimization control system comprises a pulverized coal boiler system and a DCS control system connected to the pulverized coal boiler system and used to control combustion adjustment of the pulverized coal boiler system; the pulverized coal boiler system comprises a boiler, a pulverized coal inlet of the boiler is connected to a coal mill, and a pulverized coal outlet of the coal mill is provided with a dynamic separator; an SCR system is provided inside the boiler; electrostatic precipitators are connected to both sides of the boiler through flue gas emission pipes, wherein each electrostatic precipitator is provided with an online measurement device for carbon content in fly ash, and the output end of the online measurement device for carbon content in fly ash is connected to the input end of the DCS control system.

[0007] Preferably, the fly ash carbon content online measuring device is arranged on an ash hopper with a large amount of ash falling in the electric field of each electrostatic precipitator.

[0008] A pulverized coal boiler combustion optimization control method, characterized by comprising the following steps:

[0009] S1. The DCS control system collects the carbon content of fly ash and processes it differently based on the values of the online carbon content measuring devices on the electrostatic precipitators on both sides of the boiler to complete the air distribution on both sides of the boiler;

[0010] S2. Change the NO x NO concentration converted to 6% O2 x Concentration (mg / Nm 3 ) and input into the DCS control system for power supply cost calculation and guidance of combustion adjustment;

[0011] S3. According to the carbon content of fly ash, NO x The generated amount is used to conduct combustion optimization experiments and the optimal operating condition is selected and recorded as the typical operating condition;

[0012] S4. Set the typical operating condition as the air distribution mode for the pulverized coal boiler system.

[0013] Preferably, in step S1, when the fly ash carbon content deviation is greater than 30%, the operating oxygen amount of the boiler on the side with the larger fly ash carbon content is first increased, and the air distribution is uniformly adjusted after the deviation on both sides is less than 30%; when the fly ash carbon content deviation is less than 30%, the fly ash carbon content is taken as the average of the fly ash carbon content on both sides, and the air distribution mode on both sides of the boiler is uniformly adjusted.

[0014] Preferably, in step S3, when the working condition is stable for 4 hours, the carbon content of fly ash is less than 2.0% and NO x The amount generated is less than 300mg / Nm 3 When the temperature is 6% O2, there is no need to continue the combustion optimization test and it can be directly recorded as a typical operating condition.

[0015] Preferably, the conventional objects optimized in step S3 are the operating oxygen content and the burnout air rate. When the operating conditions are stable for 4 hours, the fly ash carbon content is greater than 5.0% and the NO x The amount generated is greater than 450mg / Nm 3 (6% O2), under the premise of ensuring safety, increase the mill outlet temperature and dynamic separator speed, and then adjust the oxygen content and burnout air rate when these two indicators are optimal.

[0016] Due to the adoption of the above technical solution, the technical progress achieved by the present invention is as follows.

[0017] The present invention installs an online measuring device for the carbon content of fly ash on the electrostatic precipitators on both sides of the boiler, and uses a DCS control system to measure the carbon content of fly ash and NO x The combustion optimization experiment was carried out on the generated amount and the optimal operating condition was selected and recorded as the typical operating condition. The typical operating condition was then set as the air distribution mode for the pulverized coal boiler system, which can effectively reduce the carbon content of fly ash and NO x The production volume can be increased, the blending ratio of economic coal types can be improved, and huge economic benefits can be generated. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1This is the combustion optimization logic control diagram of the present invention. DETAILED DESCRIPTION

[0019] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0020] A pulverized coal boiler combustion optimization control system comprises a pulverized coal boiler system and a DCS control system connected to the pulverized coal boiler system. The DCS control system is used to control the combustion adjustment of the pulverized coal boiler system.

[0021] The pulverized coal boiler system includes a boiler, the pulverized coal inlet of the boiler is connected to a pulverizer, and the pulverized coal outlet of the pulverized coal mill is provided with a dynamic separator; an SCR system is provided inside the boiler, and the SCR system is used for denitrification of flue gas; flue gas discharge ports are provided on both sides of the boiler, and the flue gas discharge ports are connected to flue gas discharge pipes, and electrostatic precipitators are provided on the flue gas discharge pipes.

[0022] Each electrostatic precipitator is equipped with an online fly ash carbon content measurement device. This device uses spectrum analysis, and its output is connected to the input of the DCS control system. The device is installed in the hopper of the electrostatic precipitator, where the electric field has a high ash droplet volume, to ensure representative fly ash sampling. The device is installed at the constriction of the hopper and is installed horizontally.

[0023] The measurement cycle of the online measurement device for fly ash carbon content is 5 minutes, and the measurement accuracy is controlled within 0.5%. When the ash hopper temperature is higher than the acid dew point, there is no need to install a heating device. When the ash hopper temperature is lower than the acid dew point, it is necessary to install a heating device or blow it frequently with hot air to avoid ash accumulation and scaling in the sampling device.

[0024] A pulverized coal boiler combustion optimization control method comprises the following steps:

[0025] S1. The DCS control system collects the carbon content of fly ash and processes it differently based on the different values of the fly ash carbon content online measuring devices on the electrostatic precipitators on both sides of the boiler to complete the air distribution on both sides of the boiler.

[0026] After the DCS control system collects the fly ash carbon content values on both sides of the boiler, it first calculates the relative deviation of the values on both sides. When the relative deviation on both sides is greater than 30%, the operating oxygen content on the side with higher fly ash carbon content is directly increased to select the optimal operating oxygen content on one side. If the deviation on both sides is still greater than 30% after the air distribution adjustment, adjustments are made separately according to the specific conditions of both sides, and an early warning notification is issued to remind maintenance personnel to conduct cause analysis.

[0027] When the relative deviation between the two sides is less than 30%, the fly ash carbon content value is taken as the average value of the fly ash carbon content on both sides, and the combustion adjustment is performed uniformly.

[0028] S2. Change the NO x NO concentration converted to 6% O2 x Concentration (mg / Nm 3 ) and input into the DCS control system for power supply cost calculation and to guide combustion adjustment.

[0029] NO x The amount of NO generated is taken from the inlet of the SCR system x The concentration of NO was converted to 6% O2. x Concentration (mg / Nm 3 ), and then input into the DCS control system for power supply cost calculation and guidance of combustion adjustment.

[0030] S3. According to the carbon content of fly ash, NO x The combustion optimization experiment is carried out on the generated amount and the optimal operating condition is selected and recorded as the typical operating condition.

[0031] like Figure 1 As shown in the figure, when the working condition is stable for 4 hours, the carbon content of fly ash is less than 2.0% and NO x The amount generated is less than 300mg / Nm 3 When the O2 content is 6% (6%), there is no need to continue the combustion optimization test and it can be directly recorded as a typical operating condition, which can be used for operation guidance under the same operating conditions.

[0032] When the carbon content of fly ash is greater than 5.0% and NO x The amount generated is greater than 450mg / Nm 3 When the O2 content is 6% (6%), the priority is to increase the air-powder temperature at the pulverizer outlet and the speed of the pulverizer dynamic separator to reduce the carbon content of fly ash and NOx, while ensuring the safety of the pulverizing system and meeting the rated load output. x Amount generated.

[0033] In other cases, it is recommended to adjust the operating oxygen content and burnout air rate to reduce the carbon content and NO in fly ash. x When adjusting the generation amount, the operating oxygen amount adjustment step is 0.3%. When adjusting the burnout air rate, the burnout air damper opening can be increased simultaneously and the secondary air box damper opening can be reduced with an adjustment step of 10% until the opening reaches 100%.

[0034] Combustion adjustment is a fine adjustment, ignoring the impact on safety, based on the carbon content of fly ash and NO x The lowest power supply cost caused by the generated amount is used as the judgment basis, and the best air distribution plan is selected and recorded as a typical operating condition, which can be used for general operating guidance.

[0035] The impact of fly ash carbon content on the cost of coal-fired power generation is as follows: Where C 燃煤 is the change in coal-fired power generation cost caused by the carbon content of fly ash, RMB / (kW·h); W as,ar W is the basic ash content of the coal fed into the furnace, %; c,rs，m is the carbon content of fly ash, %; Q net,ar is the low calorific value of the coal fed into the furnace, kJ / kg; p 燃煤 is the unit price of coal, in yuan / t. This calculation formula comprehensively considers the impact of changes in coal type and quality, as well as changes in the proportion of economic coal blends, on power supply costs.

[0036] NO x The relationship between the production volume and the cost of liquid ammonia is: Where C 液氨 NO x Liquid ammonia cost caused by production, yuan / (kW·h); NO x Generation amount (6% oxygen content), mg / Nm 3 ;M NO is the molar mass of NO, g / mol; is the molar mass of NH3, g / mol; S is the ammonia nitrogen ratio; p 液氨 is the unit price of liquid ammonia, RMB / t. The calculation formula is adjusted based on emission standards and changes in ammonia slip.

[0037] S4. Set the typical operating condition as the air distribution mode for the pulverized coal boiler system.

[0038] When used, the present invention can effectively reduce the carbon content of fly ash, NO x Increasing the amount of coal produced and improving the blending ratio of economic coal types can produce huge economic benefits.

Claims

1. A pulverized coal boiler combustion optimization control method based on a pulverized coal boiler combustion optimization control system, characterized by: The pulverized coal boiler combustion optimization control system includes a pulverized coal boiler system and a DCS control system connected to the pulverized coal boiler system and used to control the combustion adjustment of the pulverized coal boiler system; the pulverized coal boiler system includes a boiler, the pulverized coal inlet of the boiler is connected to a coal mill, and the pulverized coal outlet of the coal mill is provided with a dynamic separator; an SCR system is provided inside the boiler; electrostatic precipitators are connected to both sides of the boiler through flue gas emission pipes, and each electrostatic precipitator is provided with an online measurement device for the carbon content of fly ash, and the output end of the online measurement device for the carbon content of fly ash is connected to the input end of the DCS control system; The pulverized coal boiler combustion optimization control method comprises the following steps S1. The DCS control system collects the carbon content of fly ash and processes it differently based on the values of the online carbon content measuring devices on the electrostatic precipitators on both sides of the boiler to complete the air distribution on both sides of the boiler; S2. Change the NO x NO concentration converted to 6% O2 x Concentration (mg / Nm 3 ) and input into the DCS control system for power supply cost calculation and guidance of combustion adjustment; S3. According to the carbon content of fly ash, NO x The generated amount is used to conduct combustion optimization experiments and the optimal operating condition is selected and recorded as the typical operating condition; S4. Set the typical operating condition as the air distribution mode for the pulverized coal boiler system.

2. The method for optimizing the combustion of a pulverized coal boiler based on the pulverized coal boiler combustion optimization control system according to claim 1, characterized in that: The on-line measuring device for the carbon content of fly ash is arranged on an ash hopper of each electrostatic precipitator where the amount of ash falling in the electric field is large.

3. The method for optimizing the combustion of a pulverized coal boiler based on the pulverized coal boiler combustion optimization control system according to claim 1, characterized in that: In step S1, when the deviation of the fly ash carbon content on both sides of the flue is greater than 30%, the operating oxygen amount of the boiler on the side with the larger fly ash carbon content is first increased, and the air distribution is uniformly adjusted after the deviation on both sides is less than 30%; when the fly ash carbon content deviation is less than 30%, the fly ash carbon content is taken as the average of the fly ash carbon content on both sides, and the air distribution mode on both sides of the boiler is uniformly adjusted.

4. The method for optimizing the combustion of a pulverized coal boiler based on the pulverized coal boiler combustion optimization control system according to claim 1, characterized in that: In step S3, when the working condition is stable for 4 hours, the carbon content of fly ash is less than 2.0% and NO x The amount generated is less than 300mg / Nm 3 When the pressure is below 6% O2, there is no need to continue the combustion optimization test and it can be directly recorded as a typical operating condition.

5. The method for optimizing the combustion of a pulverized coal boiler based on the pulverized coal boiler combustion optimization control system according to claim 1, characterized in that: The conventional objects optimized in step S3 are the operating oxygen content and the burnout air rate. When the operating conditions are stable for 4 hours, the fly ash carbon content is greater than 5.0% and the NO x The amount generated is greater than 450mg / Nm 3 (6% O2), under the premise of ensuring safety, increase the mill outlet temperature and dynamic separator speed, and adjust the oxygen content and burnout air rate when these two indicators are optimal.

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