阅读说明：本技术 一种锅炉掺烧劣质煤防结焦方法 (Method for preventing coking of boiler doped with burning inferior coal ) 是由 刘彦鹏 常征 李皓宇 王路路 李志强 王欢 郭艳平 于 2020-04-10 设计创作，主要内容包括：本发明涉及一种锅炉掺烧劣质煤防结焦方法,包括：针对从下层燃烧器到上面NOx喷口的前后墙水冷壁,易结焦的煤进入锅炉燃烧,锅炉炉膛温度整体较高造成的结焦,对燃烧器进行检查消缺,对水冷壁进行彻底的清除,消除设备缺陷,重新将内外二次风叶片调到合理的位置,加装炉膛最下排吹灰器预留孔部位的吹灰器,以加强炉膛高温区域的吹灰能力,避免或减轻炉膛高温区域的结焦；针对煤灰中钠的质量分数高造成的结焦,在启、停磨煤机过程中,缓慢操作,维持一次风压相对稳定,以减少对炉内燃烧的干扰,避免一次风压剧烈变化造成炉内结焦。本发明提高了锅炉运行的安全性及可靠性。(The invention relates to a method for preventing coking of boiler doped poor-quality coal, which comprises the following steps: aiming at the water-cooled walls of the front wall and the rear wall of the NOx nozzle from the lower layer burner to the upper surface, coal which is easy to coke enters a boiler for combustion, coking caused by the integral high temperature of a boiler hearth is detected and eliminated, the water-cooled walls are thoroughly cleaned, the defects of equipment are eliminated, the inner secondary air blade and the outer secondary air blade are adjusted to reasonable positions again, and soot blowers at the reserved holes of the soot blowers at the lowest row of the hearth are additionally arranged to strengthen the soot blowing capability of the high-temperature area of the hearth and avoid or reduce coking of the high-temperature area of the hearth; aiming at coking caused by high mass fraction of sodium in coal ash, the coal mill is slowly operated in the process of starting and stopping the coal mill, and primary air pressure is kept relatively stable so as to reduce the interference on combustion in the furnace and avoid coking in the furnace caused by severe change of the primary air pressure. The invention improves the safety and reliability of the boiler operation.)

1. A boiler poor-quality coal-doped anti-coking method is characterized by comprising the following steps:

aiming at the water-cooled walls of the front wall and the rear wall of the NOx nozzle from the lower layer burner to the upper surface, coal which is easy to coke enters a boiler for combustion, coking caused by the integral high temperature of a boiler hearth is detected and eliminated, the water-cooled walls are thoroughly cleaned, the defects of equipment are eliminated, the inner secondary air blade and the outer secondary air blade are adjusted to reasonable positions again, and soot blowers at the reserved holes of the soot blowers at the lowest row of the hearth are additionally arranged to strengthen the soot blowing capability of the high-temperature area of the hearth and avoid or reduce coking of the high-temperature area of the hearth;

aiming at coking caused by high mass fraction of sodium in coal ash, the coal mill is slowly operated in the process of starting and stopping the coal mill, and primary air pressure is kept relatively stable so as to reduce the interference on combustion in the furnace and avoid coking in the furnace caused by severe change of the primary air pressure.

2. The method for preventing coking of poor-quality coal mixed in a boiler according to claim 1, further comprising:

guide baffles are arranged in the primary air nozzles and the secondary air nozzles of each layer to enable the jet flow to deflect reversely, and the aim of reducing the diameter of the imaginary tangent circle is achieved by changing the angle of the jet flow, so that the slag bonding of the water-cooled wall is reduced; the field inspection of the soot blower is enhanced, the soot blower is blown to each heating surface strictly according to the operation rule, and the soot blower is timely withdrawn by hand operation due to leakage, jamming or program control failure, so that the furnace tube is prevented from being blown out and the soot blower is prevented from being burnt out; arranging a small number of soot blowers for overhaul in turn, and keeping the high availability ratio of the soot blowers; the slag discharging equipment is repaired immediately when the fault occurs, and the slag piling phenomenon in the cold ash hopper is prevented.

3. The method for preventing coking of poor-quality coal mixed in a boiler according to claim 1, further comprising:

aiming at the conditions that the coal water content is high, the outlet temperature of the coal mill is reduced, the coal powder cannot be rapidly combusted, the ignition distance of the coal powder is increased, the flame center is present at the outlet of a hearth, the coking of a heating surface is aggravated, and the temperature of flue gas at the outlet of the hearth is increased, and the measure of increasing the outlet temperature of the coal mill is taken.

4. The method for preventing coking of poor-quality coal mixed in a boiler according to claim 1, further comprising:

optimizing the operation of the boiler specifically comprises the following steps:

setting a wind-coal ratio curve, and automatically matching the ventilation volume of the coal mill according to the output of the coal feeder; primary air pressure is reduced;

the oxygen content at the inlet of a dial plate air preheater is used as an operating oxygen content monitoring value, and the automatic control of the air supply quantity is realized according to a given oxygen content control curve, so that the blindness of air quantity operation is avoided, and the oxygen content deviation at the left side and the right side is controlled to be not more than 0.5%; improving the oxygen content in the flue gas;

leveling secondary air blades outside the combustor to ensure uniform oxygen amount at the outlet of the combustor on the same layer;

the opening of the over-fire air is operated according to a high limit, and when CO at a desulfurization outlet is higher than 800ppm, the operation is operated according to a low limit;

the heat load of the burner is ensured to be uniform through primary air leveling;

the single-grinding high-output operation is avoided;

the speed of the same pulverized coal flow which is milled out is kept uniform;

controlling the rotating speed of the dynamic separator or the opening of a baffle of the static separator to reduce the fineness of the pulverized coal;

and the soot blowing frequency is improved.

5. The method for preventing coking of poor-quality coal mixed in a boiler according to claim 1, further comprising:

the method comprises the steps of establishing a boiler coking early warning platform, accessing real-time operation data of a unit by using a DCS (distributed control system) of a power plant, monitoring and analyzing and calculating the ash deposition and slagging of each main convection heating surface of the boiler, the temperature of flue gas at the outlet of a hearth and the temperature of flue gas at the bottom of a screen type superheater of the boiler on line based on the integral and local energy and mass balance principles of the boiler, visually displaying the operation condition and the pollution degree of the main heating surface of the boiler, providing real-time contamination pictures and boiler coking state early warning according to the operation condition of the unit, and enabling early warning results to be referenced by operators and participate in guiding soot.

6. The method for preventing coking of poor-quality coal doped in a boiler according to claim 5, wherein the boiler coking early warning platform provides a function of displaying the temperature of flue gas in the boiler, realizes calculation and monitoring of the temperature of the flue gas in the boiler in real time, calculates the temperature of flue gas at the outlet of a hearth and the average temperature of the flue gas at the inlet and the outlet of other heating surfaces, and draws a distribution diagram of the temperature of the flue gas so that operating personnel can monitor the distribution of the temperature of the flue gas in the boiler in real time.

7. The method for preventing coking of poor-quality coal mixed in boiler according to claim 6, wherein the boiler coking early warning platform displays the calculation result of ash fusion point of coal used in boiler and the recommended value of optimal coal mixing ratio of unit according to the input data of ash components of coal.

8. The method for preventing coking of poor-quality coal mixed in a boiler according to claim 1, further comprising:

establishing a boiler main heating surface contamination model, representing the soot deposition contamination state of the heating surface by using the contamination rate, calculating the contamination rate of each heating surface section by section from the exit of the economizer by using real-time working medium side parameters of unit operation and flue gas side parameters behind the economizer according to the principle of heat balance of the whole boiler and each local heating surface, and reversing the flow of the flue gas from the exit of the economizer to judge the boiler screen bottom coking state.

Technical Field

The invention belongs to the technical field of safe operation of thermal power plants, and particularly relates to a method for preventing coking of boiler doped poor-quality coal.

Background

The coke is mainly formed by that molten or partially molten particles carried in flue gas collide on a furnace wall, a water-cooled wall or a pipe to be cooled and solidified, the form of the coke mainly appears in the form of viscous or molten precipitates, and the coke mainly appears on a radiation heating surface.

In recent years, in order to save fuel cost, many power plants in China burn a large amount of low-quality coal, especially high-sulfur and high-alkali coal, so that the coking phenomenon of a boiler is aggravated, and severe coking has adverse effects on the safety and the economical efficiency of boiler operation. Therefore, a method for preventing coking of boiler doped with poor quality coal is needed.

Disclosure of Invention

The invention aims to provide a method for preventing coking of boiler doped with poor-quality coal, so as to ensure the safety of boiler operation.

The invention provides a method for preventing coking of boiler doped inferior coal, which comprises the following steps:

aiming at the water-cooled walls of the front wall and the rear wall of the NOx nozzle from the lower layer burner to the upper surface, coal which is easy to coke enters a boiler for combustion, coking caused by the integral high temperature of a boiler hearth is detected and eliminated, the water-cooled walls are thoroughly cleaned, the defects of equipment are eliminated, the inner secondary air blade and the outer secondary air blade are adjusted to reasonable positions again, and soot blowers at the reserved holes of the soot blowers at the lowest row of the hearth are additionally arranged to strengthen the soot blowing capability of the high-temperature area of the hearth and avoid or reduce coking of the high-temperature area of the hearth;

aiming at coking caused by high mass fraction of sodium in coal ash, the coal mill is slowly operated in the process of starting and stopping the coal mill, and primary air pressure is kept relatively stable so as to reduce the interference on combustion in the furnace and avoid coking in the furnace caused by severe change of the primary air pressure.

Further, the method further comprises:

guide baffles are arranged in the primary air nozzles and the secondary air nozzles of each layer to enable the jet flow to deflect reversely, and the aim of reducing the diameter of the imaginary tangent circle is achieved by changing the angle of the jet flow, so that the slag bonding of the water-cooled wall is reduced; the field inspection of the soot blower is enhanced, the soot blower is blown to each heating surface strictly according to the operation rule, and the soot blower is timely withdrawn by hand operation due to leakage, jamming or program control failure, so that the furnace tube is prevented from being blown out and the soot blower is prevented from being burnt out; arranging a small number of soot blowers for overhaul in turn, and keeping the high availability ratio of the soot blowers; the slag discharging equipment is repaired immediately when the fault occurs, and the slag piling phenomenon in the cold ash hopper is prevented.

Further, the method further comprises:

aiming at the conditions that the coal water content is high, the outlet temperature of the coal mill is reduced, the coal powder cannot be rapidly combusted, the ignition distance of the coal powder is increased, the flame center is present at the outlet of a hearth, the coking of a heating surface is aggravated, and the temperature of flue gas at the outlet of the hearth is increased, and the measure of increasing the outlet temperature of the coal mill is taken.

Further, the method further comprises:

optimizing the operation of the boiler specifically comprises the following steps:

setting a wind-coal ratio curve, and automatically matching the ventilation volume of the coal mill according to the output of the coal feeder; primary air pressure is reduced;

the oxygen content at the inlet of a dial plate air preheater is used as an operating oxygen content monitoring value, and the automatic control of the air supply quantity is realized according to a given oxygen content control curve, so that the blindness of air quantity operation is avoided, and the oxygen content deviation at the left side and the right side is controlled to be not more than 0.5%; improving the oxygen content in the flue gas;

leveling secondary air blades outside the combustor to ensure uniform oxygen amount at the outlet of the combustor on the same layer;

the opening of the over-fire air is operated according to a high limit, and when CO at a desulfurization outlet is higher than 800ppm, the operation is operated according to a low limit;

the heat load of the burner is ensured to be uniform through primary air leveling;

the single-grinding high-output operation is avoided;

the speed of the same pulverized coal flow which is milled out is kept uniform;

controlling the rotating speed of the dynamic separator or the opening of a baffle of the static separator to reduce the fineness of the pulverized coal;

and the soot blowing frequency is improved.

Further, the method further comprises:

the method comprises the steps of establishing a boiler coking early warning platform, accessing real-time operation data of a unit by using a DCS (distributed control system) of a power plant, monitoring and analyzing and calculating the ash deposition and slagging of each main convection heating surface of the boiler, the temperature of flue gas at the outlet of a hearth and the temperature of flue gas at the bottom of a screen type superheater of the boiler on line based on the integral and local energy and mass balance principles of the boiler, visually displaying the operation condition and the pollution degree of the main heating surface of the boiler, providing real-time contamination pictures and boiler coking state early warning according to the operation condition of the unit, and enabling early warning results to be referenced by operators and participate in guiding soot.

Furthermore, the boiler coking early warning platform provides a boiler internal flue gas temperature display function, realizes calculation and monitoring of the boiler internal real-time flue gas temperature, calculates the furnace outlet flue gas temperature and the average flue gas temperature of inlets and outlets of other heating surfaces, and draws a flue gas temperature distribution diagram so that operating personnel can monitor the boiler internal flue gas temperature distribution in real time.

Further, the boiler coking early warning platform displays the calculation result of the ash fusion point of the coal used for the boiler and the optimal coal blending proportion recommended value of the unit according to the input data of the ash components of the coal.

Further, the method further comprises:

establishing a boiler main heating surface contamination model, representing the soot deposition contamination state of the heating surface by using the contamination rate, calculating the contamination rate of each heating surface section by section from the exit of the economizer by using real-time working medium side parameters of unit operation and flue gas side parameters behind the economizer according to the principle of heat balance of the whole boiler and each local heating surface, and reversing the flow of the flue gas from the exit of the economizer to judge the boiler screen bottom coking state.

By means of the scheme, the safety and the reliability of the operation of the boiler are improved by the method for preventing coking by mixing the inferior coal with the boiler.

The foregoing is a summary of the present invention, and in order to provide a clear understanding of the technical means of the present invention and to be implemented in accordance with the present specification, the following is a detailed description of the preferred embodiments of the present invention.

Detailed Description

The following examples are given to further illustrate the embodiments of the present invention. The following examples are intended to illustrate the invention but are not intended to limit the scope of the invention.

The embodiment provides a method for preventing coking of boiler doped poor-quality coal, which comprises the following steps:

aiming at the water-cooled walls of the front wall and the rear wall of the NOx nozzle from the lower layer burner to the upper surface, coal which is easy to coke enters a boiler for combustion, coking caused by the integral high temperature of a boiler hearth is detected and eliminated, the water-cooled walls are thoroughly cleaned, the defects of equipment are eliminated, the inner secondary air blade and the outer secondary air blade are adjusted to reasonable positions again, and soot blowers at the reserved holes of the soot blowers at the lowest row of the hearth are additionally arranged to strengthen the soot blowing capability of the high-temperature area of the hearth and avoid or reduce coking of the high-temperature area of the hearth;

aiming at coking caused by high mass fraction of sodium in coal ash, the coal mill is slowly operated in the process of starting and stopping the coal mill, and primary air pressure is kept relatively stable so as to reduce the interference on combustion in the furnace and avoid coking in the furnace caused by severe change of the primary air pressure.

In this embodiment, the method further includes:

the guide baffle plates are arranged in the primary air nozzle and the secondary air nozzle of each layer to enable the jet flow to deflect reversely, and the aim of reducing the diameter of the imaginary tangent circle is achieved by changing the angle of the jet flow, so that the slag bonding of the water-cooled wall is reduced. The primary wind speed has great influence on jet flow rigidity, the primary wind speed is improved, the rigidity of primary wind jet flow can be effectively enhanced, the deviation caused by the static pressure difference at two sides of the jet flow is avoided, and the slag bonding caused by the fact that the primary wind jet flow directly impacts a wall is also avoided.

The field inspection of the soot blower is enhanced, the soot blower is blown to each heating surface strictly according to the operation rule, and the soot blower is timely withdrawn by hand operation due to leakage, jamming or program control failure, so that the furnace tube is prevented from being blown out and the soot blower is prevented from being burnt out; arranging a small number of soot blowers for overhaul in turn, and keeping the high availability ratio of the soot blowers; the slag discharging equipment is repaired immediately when the fault occurs, and the slag piling phenomenon in the cold ash hopper is prevented.

In this embodiment, the method further includes:

aiming at the conditions that the coal water content is high, the outlet temperature of the coal mill is reduced, the coal powder cannot be rapidly combusted, the ignition distance of the coal powder is increased, the flame center is present at the outlet of a hearth, the coking of a heating surface is aggravated, and the temperature of flue gas at the outlet of the hearth is increased, and the measure of increasing the outlet temperature of the coal mill is taken.

In this embodiment, the method further includes:

optimizing the operation of the boiler specifically comprises the following steps:

setting a wind-coal ratio curve, and automatically matching the ventilation volume of the coal mill according to the output of the coal feeder; primary air pressure is reduced;

the oxygen content at the inlet of a dial plate air preheater is used as an operating oxygen content monitoring value, and the automatic control of the air supply quantity is realized according to a given oxygen content control curve, so that the blindness of air quantity operation is avoided, and the oxygen content deviation at the left side and the right side is controlled to be not more than 0.5%; improving the oxygen content in the flue gas;

leveling secondary air blades outside the combustor to ensure uniform oxygen amount at the outlet of the combustor on the same layer;

the opening of the over-fire air is operated according to a high limit, and when CO at a desulfurization outlet is higher than 800ppm, the operation is operated according to a low limit;

the heat load of the burner is ensured to be uniform through primary air leveling;

the single-grinding high-output operation is avoided;

the speed of the same pulverized coal flow which is milled out is kept uniform;

controlling the rotating speed of the dynamic separator or the opening of a baffle of the static separator to reduce the fineness of the pulverized coal;

and the soot blowing frequency is improved.

For the slag bonding condition at the bottom of the screen, the flame center is reduced in the operation process, the temperature at the bottom end of the screen is reduced, and the slag bonding tendency is reduced.

In this embodiment, the method further includes:

the method comprises the steps of establishing a boiler coking early warning platform, accessing real-time operation data of a unit by using a DCS (distributed control system) of a power plant, monitoring and analyzing and calculating the ash deposition and slagging of each main convection heating surface of the boiler, the temperature of flue gas at the outlet of a hearth and the temperature of flue gas at the bottom of a screen type superheater of the boiler on line based on the integral and local energy and mass balance principles of the boiler, visually displaying the operation condition and the pollution degree of the main heating surface of the boiler, providing real-time contamination pictures and boiler coking state early warning according to the operation condition of the unit, and enabling early warning results to be referenced by operators and participate in guiding soot.

In this embodiment, the boiler coking early warning platform provides a boiler internal flue gas temperature display function, realizes calculation and monitoring of the boiler internal real-time flue gas temperature, calculates the furnace outlet flue gas temperature and the average flue gas temperature of the inlet and outlet of each heating surface, and draws a flue gas temperature distribution diagram, so that the operating personnel can monitor the boiler internal flue gas temperature distribution in real time.

In this embodiment, the boiler coking early warning platform displays the calculation result of the ash fusion point of the coal used in the boiler and the recommended value of the optimal coal blending proportion of the unit according to the input data of the ash components of the coal.

The boiler coking early warning platform calculates and makes corresponding coking tendency according to coal-fired condition and platen superheater bottom temperature and distinguishes to the realization is to the boiler screen bottom coking carry out the early warning, and it is biggest to reach the boiler and mix burning the economic income of inferior coal under the prerequisite of guaranteeing boiler safety, environmental protection finally. The boiler coking early warning platform is put into use to achieve the purposes of saving energy, reducing consumption and improving the operating economy and safety of the unit.

In this embodiment, the method further includes:

establishing a boiler main heating surface contamination model, representing the soot deposition contamination state of the heating surface by using the contamination rate, calculating the contamination rate of each heating surface section by section from the exit of the economizer by using real-time working medium side parameters of unit operation and flue gas side parameters behind the economizer according to the principle of heat balance of the whole boiler and each local heating surface, and reversing the flow of the flue gas from the exit of the economizer to judge the boiler screen bottom coking state.

In the operation of the boiler, for a certain heating surface heat exchange tube, working media flow in the tube, and smoke flows outside the tube. In the process, the flue gas environment is complex, and the contamination is easy to occur outside the heating surface heat exchange tube, and the principle of establishing a contamination model is briefly described below.

The contamination rate introduced into the furnace here is given by the formula:

in the formula, x_pjPsi being an ideal (uncontaminated) heat transfer coefficient for the heated surface_pjThe average thermal effective coefficient of the hearth is as follows:

the method for calculating the smoke temperature at the outlet of the hearth comprises the following steps:

in the formula, T_a-a theoretical combustion temperature;

m is a constant of the central position of the flame and is related to the structure of the hearth;

σ₀boltzmann constant, 5.67 × 10^-8；

a_l-furnace blackness, representing the hypothetical blackness of the effective radiation of the flame;

F_lt-furnace area;

-a heat retention coefficient;

B_j-calculating the amount of fuel;

average heat capacity of combustion products

The basis of the contamination model is based on energy balance and mass balance under the stable working condition of the unit, and when the unit is in a quick working condition, the calculated value of the system has larger deviation. In order to avoid misleading operators, the system judges whether the generator set is in positive variable load operation or not by calculating the slope of the generated power, and prompts the unit set that the pollution rate curve in the rapid variable load process fluctuates when the rapid variable working condition is determined.

The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, it should be noted that, for those skilled in the art, many modifications and variations can be made without departing from the technical principle of the present invention, and these modifications and variations should also be regarded as the protection scope of the present invention.