CN217816771U - Tail flue system of pure-combustion sludge circulating fluidized bed boiler - Google Patents

Abstract

The invention discloses a tail flue system of a pure sludge-fired circulating fluidized bed boiler, which solves the problems that the tail heating surface of the existing circulating fluidized bed boiler is easy to stain and corrode and slag is serious when sludge is combusted. A high-temperature overheating screen (11) is arranged in the dilute phase zone of the hearth; the other end of the horizontal flue (18) is connected with a first tail flue (19), and the outlet of a third tail flue (25) is communicated with a chimney through a bag type dust collector; a water-cooling evaporation tube bundle (20), a medium-temperature superheater (21), a low-temperature superheater (22) and a high-temperature economizer (23) are sequentially arranged in a first tail flue (19), a high-temperature electric dust remover (24) is arranged in a second tail flue, and a desulfurization catalyst (26), a low-temperature economizer (27), a high-temperature air preheater (28) and a low-temperature air preheater (29) are sequentially arranged in a third tail flue; the influence of corrosion on the boiler is minimized.

Description

Tail flue system of pure-combustion sludge circulating fluidized bed boiler

Technical Field

The invention relates to a circulating fluidized bed boiler, in particular to a tail flue system of a circulating fluidized bed boiler which only uses sludge as fuel.

Background

With the development of economy, the amount of sludge generated in production and life is continuously increased, and the sludge disposal pressure is increased; because the sludge contains toxic and harmful substances such as pathogens, heavy metals, persistent organic matters and the like, if the sludge is not treated well, secondary pollution is easily caused to underground water, soil and the like; after being dried, the sludge is burnt, and the burnt ash is used as a building material, so that the sludge effective disposal scheme is gradually formed; the sludge drying incineration can realize the higher reduction, stabilization and harmlessness of the sludge to the maximum extent, and the circulating fluidized bed boiler becomes available equipment for incinerating the sludge; but the sludge incineration treatment by the circulating fluidized bed boiler has a great problem; because the sludge has the characteristics of low density, high water content, lower heat value, large ash content and high heavy metal and chlorine content, when the sludge is combusted in the circulating fluidized bed boiler, the problems of hearth coking and high-temperature heating surface slagging are particularly prominent, so that the boiler cannot be stably combusted, and the continuous normal operation of the boiler is seriously influenced; the existing circulating fluidized bed boiler mainly comprises a hearth, a high-temperature cyclone separator and a tail flue, wherein the tail flue is sequentially provided with a high-temperature superheater, a low-temperature superheater, an economizer and an air preheater from top to bottom; because the sludge has high moisture content and high viscosity, the boiler combustion chamber is easy to cause coking phenomenon due to poor fluidization.

In the boiler afterbody flue of current circulating fluidized bed boiler, from last to having arranged in proper order down: the flue gas passes through an outlet flue and enters a dust remover and a chimney; when the boiler fuel is sludge, the ash content of the sludge is high, and the content of alkali metal elements is also high, so that alkali metal is easy to separate out on a high-temperature convection heating surface of a tail flue, and the heating surface is easy to stain on the tail convection heating surface, so that the pipe wall of the heating surface is corroded.

Disclosure of Invention

The invention provides a tail flue system of a pure-combustion sludge circulating fluidized bed boiler, which solves the technical problem that a tail heating surface of the existing circulating fluidized bed boiler is easy to stain, corrode and slag when sludge is combusted.

The invention solves the technical problems through the following technical scheme:

the general concept of the invention is: arranging a traditional high-temperature superheater arranged in a tail flue to a dilute phase region in a hearth, arranging three flues which are sequentially communicated end to end at the tail of a boiler, arranging a water-cooling evaporation tube bundle, a medium-temperature superheater, a low-temperature superheater and a high-temperature economizer in a first flue, arranging a high-temperature electric dust remover in a second flue, and arranging a denitrating catalyst, a low-temperature economizer, a high-temperature air preheater and a low-temperature air preheater in a third flue; the method comprises the following steps that smoke in a hearth passes through a horizontal flue at the upper part of the hearth, firstly enters a water-cooling evaporation tube bundle, the temperature of the smoke is reduced to be below 650 ℃ after passing through the water-cooling evaporation tube bundle, then passes through middle and low temperature superheaters arranged in a large-interval in-line manner, the temperature of a steam outlet of the middle temperature superheaters is designed to be below 400 ℃, so that an interval with the high-temperature corrosion activity temperature of a heated surface being more than 500 ℃ can be avoided, high-temperature coal economizers arranged in a large-interval in-line manner are arranged below the low temperature superheaters, a second tail flue is arranged at the outlet of each high-temperature coal economizer, a high-temperature electric precipitator is arranged in the second tail flue, 90% of fly ash in the smoke can be removed after the smoke passes through the high-temperature electric precipitator, a third flue is arranged behind the second tail, so that an SCR catalyst in the third flue is not quickly worn or blocked by the fly ash, the SCR catalyst is ensured to be safely used for a long time, the smoke after passing through the SCR catalyst, enters the low-temperature coal economizers arranged in a large-interval in-line manner, is relatively clean manner, and then a proper soot blowing device is matched, so that the heated surface can be effectively prevented from being contaminated and corroded; after the low-temperature economizer, the air preheater in a horizontal arrangement mode of the large-pitch in-line light pipes is adopted, and the phenomenon that the heating surface is bridged due to dust accumulation can be well avoided due to the heating surface arranged at large intervals.

A tail flue system of a pure-combustion sludge circulating fluidized bed boiler comprises a circulating fluidized bed boiler hearth and a cyclone separator, wherein a hearth dilute phase region is arranged in the circulating fluidized bed boiler hearth, a smoke outlet is formed in the circulating fluidized bed boiler hearth, the cyclone separator is connected to the smoke outlet, a horizontal flue is connected to the cyclone separator, and a high-temperature overheating screen is arranged in the hearth dilute phase region; the other end of the horizontal flue is connected with a first tail flue, a second tail flue is connected to a smoke outlet of the first tail flue, a third tail flue is connected to a smoke outlet of the second tail flue, and the smoke outlet of the third tail flue is communicated with a chimney through a bag type dust collector; in the first tail flue, a water-cooled evaporation tube bundle, a medium-temperature superheater, a low-temperature superheater and a high-temperature economizer are sequentially arranged from top to bottom, a high-temperature electric dust remover is arranged in the second tail flue, and in the third tail flue, a denitration catalyst, a low-temperature economizer, a high-temperature air preheater and a low-temperature air preheater are sequentially arranged from top to bottom; a first flue soot blower is arranged in the first flue at the tail part, and a third flue soot blower is arranged in the third flue at the tail part.

After the flue gas discharged from the horizontal flue passes through the water-cooling evaporation tube bundle, the temperature of the flue gas is lower than 650 ℃, the temperature of a steam outlet in the medium-temperature superheater is lower than 400 ℃, and a tube of the low-temperature air preheater is made of an enamel tube.

The invention fundamentally overcomes the defects that the tail heating surface is easy to stain, corrode and deposit dust when the existing circulating fluidized bed boiler burns sludge, so that the boiler can safely and stably operate for a long time, the influence of corrosion on the boiler is reduced to the minimum, and the safe operation of the boiler is ensured.

Drawings

FIG. 1 is a schematic diagram of the present invention.

Detailed Description

The invention is described in detail below with reference to the accompanying drawings:

a tail flue system of a pure-combustion sludge circulating fluidized bed boiler comprises a circulating fluidized bed boiler hearth and a cyclone separator, wherein a hearth dilute phase zone 10 is arranged in the circulating fluidized bed boiler hearth, a smoke outlet 12 is arranged on the circulating fluidized bed boiler hearth, the cyclone separator is connected to the smoke outlet 12, a horizontal flue 18 is connected to the cyclone separator, and a high-temperature overheating screen 11 is arranged in the hearth dilute phase zone 10; the other end of the horizontal flue 18 is connected with a first tail flue 19, a second tail flue is connected with a smoke outlet of the first tail flue 19, a third tail flue 25 is connected with a smoke outlet of the second tail flue, and the smoke outlet of the third tail flue 25 is communicated with a chimney 31 through a bag type dust collector 30; in the first tail flue 19, from top to bottom, a water-cooled evaporation tube bundle 20, a medium-temperature superheater 21, a low-temperature superheater 22 and a high-temperature economizer 23 are sequentially arranged, in the second tail flue, a high-temperature electric dust remover 24 is arranged, and in the third tail flue 25, from top to bottom, a denitrification catalyst 26, a low-temperature economizer 27, a high-temperature air preheater 28 and a low-temperature air preheater 29 are sequentially arranged; a tail first flue soot blower 34 is arranged in the tail first flue 19, and a tail third flue soot blower 35 is arranged in the tail third flue 25; after the flue gas discharged from the horizontal flue 18 passes through the water-cooling evaporation tube bundle 20, the temperature of the flue gas is lower than 650 ℃, the temperature of the steam in the medium-temperature superheater 21 is lower than 400 ℃, and the pipe of the low-temperature air preheater 29 is made of enamel pipe.

In order to avoid influencing the safety of the boiler, solidify alkali metal in ash into solid and separate out, reduce the contamination of the heating surface of the tail coiled pipe and solve the problem of contamination of the heating surface, the invention adopts the following technical measures to improve the contamination resistance of the heating surface: (1) The middle-low temperature superheater is arranged in a first tail flue, the wall temperature of the heated surface is controlled in a partitioning mode, the wall temperature of the heated surface of the tail flue is guaranteed to be less than or equal to 500 ℃, and the tail flue is separated from a chlorination corrosion activity temperature interval; (2) The high-temperature superheater is arranged in the hearth in a screen mode, adopts a corrosion-resistant TP347H pipe, and utilizes a large amount of high-concentration circulating materials in a main circulating loop of the circulating fluidized bed boiler to scour the heated surface so as to keep the surface of the heated surface clean and achieve the effect of preventing high-temperature corrosion; (3) The low-temperature section of the air preheater adopts a pipe made of an enamel pipe material, so that the corrosion resistance of the material in the low-temperature region is improved, and meanwhile, a hot air recirculation system is adopted to improve the temperature of cold air; the problem of corrosion blockage caused by low temperature condensation at a low-temperature section due to low inlet air temperature of an air preheater when the environmental temperature is low in winter is solved; (4) The corrosion allowance of the heating surface tube is improved by increasing the wall thickness of the heating surface tube, and the service life of the heating surface tube is prolonged; (5) By spraying limestone powder in the furnace, caO generated by calcining limestone can solidify partial chloride ions while the desulfurization requirement in the furnace is met, so that the concentration of active chloride ions in flue gas is reduced, and further the corrosion of a tail heating surface is reduced.

The fly ash generated after the sludge fuel is combusted has strong pollution, and the hearth has a large amount of circulating materials, so the fly ash has strong self-cleaning property and is difficult to pollute; however, after the flue gas passes through the high-temperature heat-insulation cyclone separator, the particle size of fly ash in the flue gas is thinned, the pollution property to the heating surface of the tail flue is stronger, the fly ash is easy to attach to a heating surface pipe to cause the reduction of the heat transfer effect, the rise of the exhaust gas temperature and the reduction of the boiler efficiency; the first flue and the third flue are provided with a certain amount of soot blowing devices which have good performance, reliable quality and reasonable arrangement, so that the heating surfaces of the middle-temperature superheater, the low-temperature superheater, the high-temperature economizer, the low-temperature economizer and the air preheater in the tail flue are effectively kept clean when the boiler operates; selecting a steam soot blower to blow soot with strong force, and adjusting soot blowing frequency at any time according to operation requirements; during soot blowing, soot blowing is carried out layer by layer according to the flow direction of flue gas; the second flue is provided with high-temperature electric dust removal, the flue gas entering the third flue is clean flue gas, the tail denitration catalyst is effectively prevented from being blocked, and the tail heating surface of the third flue is kept clean and the design efficiency of the boiler is kept.

A circulating fluidized bed boiler burning sludge only comprises a sludge drying bin 1, a circulating fluidized bed boiler heat insulation hearth, a cyclone separator, a first tail flue 19, a second tail flue, a third tail flue 25, a bag type dust collector 30 and a chimney 31, wherein a hearth dense-phase region negative pressure region 3 and a hearth dilute-phase region 10 are arranged in the circulating fluidized bed boiler heat insulation hearth, the cyclone separator is connected to a smoke outlet 12 of the circulating fluidized bed boiler heat insulation hearth, the cyclone separator is communicated with the first tail flue 19 through a horizontal flue 18, the second tail flue is connected to a smoke outlet of the first tail flue 19, the third tail flue 25 is connected to a smoke outlet of the second tail flue, and the smoke outlet of the third tail flue 25 is communicated with the chimney 31 through the bag type dust collector 30; the cyclone separator is formed by sequentially connecting a cylindrical barrel 14, a conical transition barrel 15, a return pipe and a return box 16 together, wherein the return box 16 is connected with a lower section 17 of the return pipe, the lower end of the lower section 17 of the return pipe is communicated with a return port 9 on a heat-insulating hearth of the circulating fluidized bed boiler, the bottom of the dried sludge bin 1 is provided with a stirring arm with an excavating claw, a discharge port of the dried sludge bin 1 is connected with a screw feeder 32, a discharge port of the screw feeder 32 is connected with a blanking pipe 33, the other end of the blanking pipe 33 is communicated with a feeding port 2 of the hearth, the feeding port 2 is arranged in a negative pressure zone 3 of a dense-phase zone of the hearth, dried sludge 8 enters the hearth through the feeding port 2, and a high-temperature overheating screen 11 is arranged in a dilute-phase zone 10 of the hearth; the ratio of the diameter of the cylindrical barrel 14 to the diameter of the return pipe is 5-10; the ratio of the height of the cylindrical barrel 14 to the height of the conical transition barrel 15 is 0.3-1, and the height of the return pipe is 2-9 m; a water-cooling evaporation tube bundle 20 is arranged in the first tail flue 19, and a high-temperature electric dust remover 24 is arranged in the second tail flue; the boiler adopts a fully heat-insulating hearth and a low-temperature combustion technology, the flow rate in the hearth is low, the flow rate in a conical section of the hearth is high, and the good air distribution and distribution plate is fluidized uniformly, so that the coking and slagging of the boiler are solved, the height of the hearth is improved, the retention time of flue gas at high temperature is increased, the rigidity of secondary air is enhanced, substances which are not completely combusted in the flue gas are fully contacted with air, and the emission of dioxin is reduced; by adopting the high-efficiency heat-insulation cyclone separator, after the flue gas passes through the separator, the particle size of fly ash in the flue gas is thinned, the amount of fly ash is reduced, and the fly ash erosion wear and dust accumulation of a heating surface in a tail flue are reduced; in addition, the high-efficiency separator enables the particle size of the circulating material in the hearth to be finer, the bed quality to be improved, and the flow state reconstruction is realized; after the bed quality is improved, the specific surface of limestone in the furnace is increased, and the desulfurization efficiency in the furnace is higher; after the bed quality is improved, the particle agglomeration capability is enhanced, and the generation amount of NOx is inhibited; a middle and high temperature screen type superheater is arranged on the front wall of the hearth, and high temperature corrosion is prevented by scouring a large amount of circulating materials in a main circulating loop of the circulating fluidized bed boiler; the temperature of flue gas entering the low-temperature superheater is reduced through an evaporation tube bundle on the upper part of the tail flue, so that the temperature of a metal wall of the low-temperature superheater is lower than a chlorination corrosion active temperature range, and the corrosion probability of the low-temperature superheater is reduced; the tail heating surface is arranged in a large-pitch, high-flow-rate and in-line manner, and a steam soot blower is assisted to prevent soot deposition; the air preheater is horizontally arranged with the light tubes arranged in the row at a large pitch, and adopts corrosion-resistant materials, so that the smoke exhaust temperature is increased, and low-temperature corrosion is avoided.

A primary air inlet 4 and a secondary air inlet 13 are respectively arranged in a hearth of the circulating fluidized bed boiler, and an air inlet hood 6 for primary air is arranged in a water-cooling air chamber 5 at the lower part of the hearth; the ratio of the primary air quantity entering the hearth through the primary air inlet 4 to the secondary air quantity entering the hearth through the secondary air inlet 13 is 45-55, and the air outlet speed of the air inlet hood 6 is 37-38 meters per second; the cyclone separator conveys the high-temperature ash particles with the particle size of more than 20 microns in the high-temperature ash particles to the hearth through the lower section 17 of the material returning pipe for circular combustion, and the cyclone separator conveys the high-temperature ash particles with the particle size of less than 20 microns to a tail vertical shaft flue through the cylindrical barrel 14; the thickness of the bed material 7 in the hearth is 400-520 mm; the high-temperature electrostatic precipitator is arranged at the outlet of the high-temperature coal economizer, 90% of fly ash in the flue gas can be removed after the flue gas passes through the high-temperature electrostatic precipitator, and the subsequent SCR catalyst can not be quickly abraded or blocked by the fly ash, so that the safe use of the catalyst is ensured; the SCR selective catalyst stably operates, so that the emission of NOx is further reduced; and then enters the low-temperature economizer, the flue gas is relatively clean, and the soot is properly blown, so that the pollution and corrosion can be effectively prevented.

In the first tail flue 19, from top to bottom, a water-cooled evaporation tube bundle 20, a medium-temperature superheater 21, a low-temperature superheater 22 and a high-temperature economizer 23 are arranged in sequence, in the second tail flue, a high-temperature electric dust remover 24 is arranged, and in the third tail flue 25, from top to bottom, a denitrating catalyst 26, a low-temperature economizer 27, a high-temperature air preheater 28 and a low-temperature air preheater 29 are arranged in sequence; a rear first-flue sootblower 34 is provided in the rear first flue 19, and a rear second-flue sootblower 35 is provided in the rear third flue 25.

After the flue gas discharged from the horizontal flue 18 passes through the water-cooling evaporation tube bundle 20, the temperature of the flue gas is lower than 650 ℃, the temperature of a steam outlet in the medium-temperature superheater 22 is lower than 400 ℃, and the corrosion area of chloride on the heating surface is ingeniously avoided by adjusting the arrangement position of each heating surface in the boiler, so that the boiler can stably and safely operate for a long time.

Claims (2)

1. A tail flue system of a pure-combustion sludge circulating fluidized bed boiler comprises a circulating fluidized bed boiler hearth and a cyclone separator, wherein a hearth dilute phase zone (10) is arranged in the circulating fluidized bed boiler hearth, a smoke outlet (12) is arranged on the circulating fluidized bed boiler hearth, the cyclone separator is connected to the smoke outlet (12), and a horizontal flue (18) is connected to the cyclone separator, and the tail flue system is characterized in that a high-temperature overheating screen (11) is arranged in the hearth dilute phase zone (10); the other end of the horizontal flue (18) is connected with a first tail flue (19), a second tail flue is connected to a smoke outlet of the first tail flue (19), a third tail flue (25) is connected to a smoke outlet of the second tail flue, and the smoke outlet of the third tail flue (25) is communicated with a chimney (31) through a bag type dust collector (30); a water-cooling evaporation tube bundle (20), a medium-temperature superheater (21), a low-temperature superheater (22) and a high-temperature economizer (23) are sequentially arranged in the first tail flue (19) from top to bottom, a high-temperature electric dust remover (24) is arranged in the second tail flue, and a denitrification catalytic device (26), a low-temperature economizer (27), a high-temperature air preheater (28) and a low-temperature air preheater (29) are sequentially arranged in the third tail flue (25) from top to bottom; a first flue soot blower (34) is arranged in the first flue (19) at the tail part, and a third flue soot blower (35) is arranged in the third flue (25) at the tail part.

2. The tail flue system of the pure combustion sludge circulating fluidized bed boiler according to claim 1, characterized in that the temperature of the flue gas discharged from the horizontal flue (18) after passing through the water-cooled evaporator tube bundle (20) is lower than 650 ℃, the temperature of the steam outlet in the medium-temperature superheater (21) is lower than 400 ℃, and the pipe of the low-temperature air preheater (29) is made of enamel pipe.

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