CN110848670A - Novel ignition mode application of 300MW circulating fluidized bed boiler - Google Patents

Abstract

A novel ignition mode of a 300MW circulating fluidized bed boiler is applied. At present, the earliest 300MW circulating fluidized bed unit in China is put into operation for many years, and the unit has high starting oil consumption due to poor quality of coal and difficult ignition. The invention is characterized in that: only start the primary air fan at the initial stage of adopting the ignition, other fans are stopped running, and the amount of wind of adjusting makes the boiler be in the novel ignition mode of little tympanic bulla state, (1) suitable bed thickness and granularity: the thickness of the material layer is controlled to be 800-900 mm, (2) cold fluidization test before starting: feeding bed materials into a hearth through a starting bed material system and a scraper coal feeder before each start of the circulating fluidized bed boiler, carrying out a fluidization test of the bed materials, (3) increasing the temperature of the boiler before ignition: the pressure of a heating heat source can be increased to 3.9MPa from 0.8MPa, (4) the heat loss during oil feeding is reduced: adjusting the pressure of a hearth outlet to 50-100 Pa through an inlet valve and an outlet valve of a draught fan, and (5) selecting a proper bed temperature to correctly feed coal. The ignition method is applied to a novel ignition mode of a 300MW circulating fluidized bed boiler.

Description

Novel ignition mode application of 300MW circulating fluidized bed boiler

The technical field is as follows:

the invention relates to a novel ignition mode application of a 300MW circulating fluidized bed boiler.

Background art:

aiming at a 300MWCFB circulating fluidized bed boiler, the earliest 300MW circulating fluidized bed unit in China at present has been put into operation for many years, and due to the fact that coal quality of coal (15% of volatile components of an air drying base, 10.1MJ/kg of low-grade calorific value of the coal, 11% of water and 65% of ash content of the air drying base) is poor, ignition is not easy, and oil consumption of unit starting is high. According to the multiple boiler starting analysis, the key of oil saving is to reduce the boiler heat loss during oil feeding, fully use the fuel oil heat to heat bed materials as far as possible, shorten the time from coal feeding to complete coal ignition, improve the boiler temperature before ignition and the like, and reduce the unit starting oil consumption; the indirect measures for influencing the oil consumption are whether the thickness and the particle size distribution of the bed material are reasonable, the heating rate of the bed material, the quantity of air distribution, the temperature rise control of refractory materials in a hearth and a separator and the like.

The unit cold starting is started according to a conventional mode, the induced draft fan, the high pressure positive blower, the secondary fan and the primary fan are all started, the heat loss is large and the power consumption of the fan is high during the ignition period of maintaining normal air volume ignition (the primary air volume is 10-13 ten thousand m3/h, and the secondary air volume is 20-30 ten thousand m 3/h), in order to practically reduce the unit starting oil consumption and the power consumption, the full discussion and certification is adopted, only the primary fan is started at the ignition initial stage to enable the boiler to be in a bubbling state novel ignition mode, the heat loss is greatly reduced during the starting period in the novel ignition mode, the unit starting power consumption is reduced, the starting mode plays a reference role in national circulating fluidized bed unit starting oil saving, and is.

Because the circulating fluidized bed boiler is designed with the air distribution plate, a certain amount of bed materials are arranged on the circulating fluidized bed boiler when the circulating fluidized bed boiler is started, primary fluidized air in an air duct combustion chamber is heated into high-temperature hot flue gas through combustion of an oil gun under the bed, and then the bed materials on a main bed are uniformly heated through an air distribution plate hood, so that the temperature of the bed layer is raised until the bed materials are heated to a temperature level higher than the minimum temperature level required by coal feeding, and a coal feeding process is realized; due to the characteristics of the circulating fluidized bed, the circulating fluidized bed boiler is different from a conventional pulverized coal furnace in structure and combustion principle, the particle size of circulating materials determines that the combustion of the circulating fluidized bed boiler cannot be instantly and quickly carried out, the starting of the circulating fluidized bed boiler can only be a slow heating process in consideration of the safe temperature rise speed of parts such as wear-resistant pouring materials and non-metal expansion joints of the boiler, and the problems of long starting time, large bed temperature fluctuation in the starting process, large starting oil consumption and the like generally exist; therefore, the aim of ignition of the circulating fluidized bed boiler is to heat bed materials to the coal feeding temperature by using the shortest time and the least amount of fuel oil to realize coal feeding, shorten the ignition time and reduce the fuel oil consumed by starting the boiler to the maximum extent on the premise of having the smallest influence on the service life of the boiler.

The invention content is as follows:

the invention aims to provide a novel ignition mode application of a 300MW circulating fluidized bed boiler, which adopts a novel ignition mode that only a primary fan is started at the initial stage of ignition to enable the boiler to be in a bubbling state, the novel ignition mode greatly reduces the heat loss during the starting period and simultaneously reduces the starting power consumption of a unit, and the starting mode plays a reference role in starting and saving oil for the circulating fluidized bed unit in China, thereby being worthy of popularization and application.

The above purpose is realized by the following technical scheme:

the utility model provides a novel ignition mode of 300MW circulating fluidized bed boiler uses, adopts the initial stage of igniteing only to start the fan once, and other fans are stopped running, and the novel ignition mode of a volume of adjusting once messenger's boiler in little bubbling state, and the method includes the following step:

(1) suitable bed thickness and particle size:

the thickness of a material layer is controlled to be 800-900 mm, bottom slag discharged from a slag bin is generally used as a bed material for the bed material, a proper bed material is selected by screening, the particle size of the bed material is controlled to be 0-10% above 6mm, 70-100% below 0.5mm and 0-20% below 0.5mm, the carbon content of the bed material is controlled to be lower than 1%, and the hearth pressure is just maintained at 4-5 Kpa in a coal feeding process by considering the consumption of the bed material in a cold fluidization test and an ignition starting process;

(2) cold fluidization test before start-up:

the method comprises the following steps that (1) bed materials in a material return leg are all discharged into main bed materials to determine the thickness of the bed materials; secondly, pre-dusting the bag-type dust collector to further reduce the loss of fine bed materials; the third step is the determination of critical fluidization air volume; fourthly, checking the uniform fluidization of the blast caps at each position through a bed material flatness test;

(3) increasing the temperature of the boiler before ignition:

the steam source for heating the boiler is changed from middle-auxiliary heating to machine-cooling, the pressure of the heating source can be increased to 3.9MPa from 0.8MPa, the wall temperature of a steam drum before ignition of the boiler reaches 150-200 ℃, meanwhile, because the temperature of the boiler is increased, water circulation is established in advance, each heating surface of the boiler is heated more uniformly, and the safety of the boiler is improved;

(4) reducing heat loss during oil dosing:

only starting a primary fan at the initial stage of ignition, maintaining the shutdown of an induced draft fan, a secondary fan, a fluidized fan and a limestone fan, keeping all valves in a closed state, adjusting the primary air volume to be 2-3 ten thousand m3/h to enable a boiler to be in a novel ignition mode in a micro-bubbling state, adjusting the pressure of a hearth outlet to be 50-100 Pa through inlet and outlet valves of the induced draft fan, reducing the heat loss, gradually starting all fans according to a starting sequence when the coal feeding condition is achieved, controlling the air volume to be normal, simultaneously improving the output of an oil gun, controlling the bed temperature to be 1-15℃/min, heating at a normal rate, and recovering the ignition mode to;

(5) selecting proper bed temperature to correctly feed coal:

the coal feeding operation is a key step in the ignition starting process, the primary air volume is properly increased before coal feeding, two coal feeders are started to start pulse test coal feeding with 5% of the rated coal feeding amount of a boiler when the bed temperature is higher than 450 ℃, the oxygen amount and the bed temperature change rate are observed after 5 minutes of operation, the coal ignition condition is judged, the coal can be continuously fed after the coal is determined to be combusted, the total coal feeding amount is controlled to be about 10-40 tons, and the bed temperature is strictly controlled within the qualified range until the fuel oil is completely stopped.

Has the advantages that:

1. the invention mainly provides a novel ignition mode application of a 300MW circulating fluidized bed boiler, which greatly reduces heat loss during starting, greatly reduces the starting oil consumption of a unit, reduces the starting power consumption of the unit by adopting a novel ignition mode on the premise of meeting the starting curve of the starting unit, reduces the starting power consumption of the unit, reduces the starting oil consumption by 30 tons (light diesel oil) for a single start of the unit, and reduces the starting power consumption by 3 ten thousand kilowatts.

The invention adopts a novel ignition mode that only a primary fan is started at the initial stage of ignition to enable the boiler to be in a bubbling state, the ignition mode can greatly reduce the heat loss during the starting period, simultaneously reduces the starting power consumption of the unit, plays a reference role in saving oil for the starting of the circulating fluidized bed unit in China, and is worthy of popularization and application.

The invention changes the steam source of heating near the boiler from middle auxiliary to machine cold, the pressure of the heating source can be increased from 0.8MPa to 3.9MPa, the wall temperature of the steam drum can reach more than 150 ℃ before the ignition of the boiler, meanwhile, because the temperature of the boiler is increased, water circulation is established in advance, the heating of each heating surface of the boiler is more uniform, and the safety of the boiler is effectively improved.

The starting mode of the invention overcomes the defects that the bed material is conveyed into a hearth by a starting bed material system through a scraper coal feeder before the circulating fluidized bed boiler is started each time, the quantity of the bed material on each side is roughly calculated manually, and the bed material quantity is not easy to control, and a fluidization test of the bed material is carried out, so that the bed material in a material return leg is completely discharged into a main bed material, and the thickness of the bed material is accurately determined; the bag-type dust remover is pre-coated with ash, so that the loss of fine bed materials is further reduced; and determining the critical fluidization air quantity to ensure that the fluidization of the blast caps at each part is uniform through the flatness test of the bed material.

The specific implementation mode is as follows:

example 1:

the utility model provides a novel ignition mode of 300MW circulating fluidized bed boiler uses, adopts the initial stage of igniteing only to start the fan once, and other fans are stopped running, and the novel ignition mode of a volume of adjusting once messenger's boiler in little bubbling state, and the method includes the following step:

(1) suitable bed thickness and particle size:

the thickness of a material layer is controlled to be 800-900 mm, bottom slag discharged from a slag bin is generally used as a bed material for the bed material, a proper bed material is selected by screening, the particle size of the bed material is controlled to be 0-10% above 6mm, 70-100% below 0.5mm and 0-20% below 0.5mm, the carbon content of the bed material is controlled to be lower than 1%, and the hearth pressure is just maintained at 4-5 Kpa in a coal feeding process by considering the consumption of the bed material in a cold fluidization test and an ignition starting process;

(2) cold fluidization test before start-up:

the method comprises the following steps that (1) bed materials in a material return leg are all discharged into main bed materials to determine the thickness of the bed materials; secondly, pre-dusting the bag-type dust collector to further reduce the loss of fine bed materials; the third step is the determination of critical fluidization air volume; fourthly, checking the uniform fluidization of the blast caps at each position through a bed material flatness test;

(3) increasing the temperature of the boiler before ignition:

the steam source for heating the boiler is changed from middle-auxiliary heating to machine-cooling, the pressure of the heating source can be increased to 3.9MPa from 0.8MPa, the wall temperature of a steam drum before ignition of the boiler reaches 150-200 ℃, meanwhile, because the temperature of the boiler is increased, water circulation is established in advance, each heating surface of the boiler is heated more uniformly, and the safety of the boiler is improved;

(4) reducing heat loss during oil dosing:

only starting a primary fan at the initial stage of ignition, maintaining the shutdown of an induced draft fan, a secondary fan, a fluidized fan and a limestone fan, keeping all valves in a closed state, adjusting the primary air volume to be 2-3 ten thousand m3/h to enable a boiler to be in a novel ignition mode in a micro-bubbling state, adjusting the pressure of a hearth outlet to be 50-100 Pa through inlet and outlet valves of the induced draft fan, reducing the heat loss, gradually starting all fans according to a starting sequence when the coal feeding condition is achieved, controlling the air volume to be normal, simultaneously improving the output of an oil gun, controlling the bed temperature to be 1-15℃/min, heating at a normal rate, and recovering the ignition mode to;

(5) selecting proper bed temperature to correctly feed coal:

the coal feeding operation is a key step in the ignition starting process, the primary air volume is properly increased before coal feeding, two coal feeders are started to start pulse test coal feeding with 5% of the rated coal feeding amount of a boiler when the bed temperature is higher than 450 ℃, the oxygen amount and the bed temperature change rate are observed after 5 minutes of operation, the coal ignition condition is judged, the coal can be continuously fed after the coal is determined to be combusted, the total coal feeding amount is controlled to be about 10-40 tons, and the bed temperature is strictly controlled within the qualified range until the fuel oil is completely stopped.

Claims (1)

1. The utility model provides a novel ignition mode of 300MW circulating fluidized bed boiler uses, characterized by: the method adopts a novel ignition mode that only a primary fan is started at the initial ignition stage, other fans are stopped, and primary air quantity is adjusted to enable a boiler to be in a micro-bubbling state, and comprises the following steps:

(1) suitable bed thickness and particle size:

the thickness of a material layer is controlled to be 800-900 mm, bottom slag discharged from a slag bin is generally used as a bed material for the bed material, a proper bed material is selected by screening, the particle size of the bed material is controlled to be 0-10% above 6mm, 70-100% below 0.5mm and 0-20% below 0.5mm, the carbon content of the bed material is controlled to be lower than 1%, and the hearth pressure is just maintained at 4-5 Kpa in a coal feeding process by considering the consumption of the bed material in a cold fluidization test and an ignition starting process;

(2) cold fluidization test before start-up:

the method comprises the following steps that (1) bed materials in a material return leg are all discharged into main bed materials to determine the thickness of the bed materials; secondly, pre-dusting the bag-type dust collector to further reduce the loss of fine bed materials; the third step is the determination of critical fluidization air volume; fourthly, checking the uniform fluidization of the blast caps at each position through a bed material flatness test;

(3) increasing the temperature of the boiler before ignition:

the steam source for heating the boiler is changed from middle-auxiliary heating to machine-cooling, the pressure of the heating source can be increased to 3.9MPa from 0.8MPa, the wall temperature of a steam drum before ignition of the boiler reaches 150-200 ℃, meanwhile, because the temperature of the boiler is increased, water circulation is established in advance, each heating surface of the boiler is heated more uniformly, and the safety of the boiler is improved;

(4) reducing heat loss during oil dosing:

only starting a primary fan at the initial stage of ignition, maintaining the shutdown of an induced draft fan, a secondary fan, a fluidized fan and a limestone fan, keeping all valves in a closed state, adjusting the primary air volume to be 2-3 ten thousand m3/h to enable a boiler to be in a novel ignition mode in a micro-bubbling state, adjusting the pressure of a hearth outlet to be 50-100 Pa through inlet and outlet valves of the induced draft fan, reducing the heat loss, gradually starting all fans according to a starting sequence when the coal feeding condition is achieved, controlling the air volume to be normal, simultaneously improving the output of an oil gun, controlling the bed temperature to be 1-15℃/min, heating at a normal rate, and recovering the ignition mode to;

(5) selecting proper bed temperature to correctly feed coal:

the coal feeding operation is a key step in the ignition starting process, the primary air volume is properly increased before coal feeding, two coal feeders are started to start pulse test coal feeding with 5% of the rated coal feeding amount of a boiler when the bed temperature is higher than 450 ℃, the oxygen amount and the bed temperature change rate are observed after 5 minutes of operation, the coal ignition condition is judged, the coal can be continuously fed after the coal is determined to be combusted, the total coal feeding amount is controlled to be about 10-40 tons, and the bed temperature is strictly controlled within the qualified range until the fuel oil is completely stopped.