CN205299491U - High flow stability's supercritical cycle fluidized bed boiler water wall under low -load - Google Patents
High flow stability's supercritical cycle fluidized bed boiler water wall under low -load Download PDFInfo
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Abstract
The utility model discloses a high flow stability's supercritical cycle fluidized bed boiler water wall under low -load relates to a circulating fluidized bed boiler, including furnace all around water -cooling wall and water -cooling mid -board, and constitute furnace all around the pipe internal diameter on the upper portion of water -cooling wall and water -cooling mid -board be greater than the internal diameter of lower part, the feedwater of boiler causes water -cooling wall and water -cooling mid -board all around respectively by common downcomer, then is caused by the connecting pipe that to assemble album case mixed, assembles the over heater that steam that album case exported caused low reaches. The utility model provides an increase water -cooling wall area and the high problem of furnace under the low mass velocity, especially, solve overcritical CFB boiler water wall flow stability decline problem under the low -load of hanging down mass velocity, prevent that water -cooling wall system negative sense feedback from taking place.
Description
Technical field
The utility model relates to the circulating fluidized bed boiler water-cooling wall system of a kind of circular fluid bed, particularly supercritical parameter.
Background technology
Super critical boiler generating set can obtain higher generating efficiency, and supercritical circulating fluidized bed boiler refers to the critical parameter (22.12MPa, 374.15 DEG C) of the pressure and temperature of the steam that boiler exports higher than water vapor. But under supercritical state, water and steam does not have the difference in physical parameter, natural circulation (or pump circulation) water screen system that the drum-downtake-water wall-drum causing the following boiler of subcritical parameter to adopt is formed cannot adopt. Supercritical boiler water-cooling wall system adopts an one through boiler, and namely the working medium in water wall (water or water vapour) once passes through water wall. In water wall, to compare subcritical boiler natural circulation (or pump circulation) lower for the mass velocity of working medium, and the situation that water wall tube is cooled by working medium is deteriorated, and the temperature of water wall tube metal is higher, it is easy to the problem that overtemperature damages occur.
Supercritical boiler water-cooling wall working medium direct current, water wall sender property outlet is superheated vapour, furnace wall cooling is at different positions, such as front water wall, side water wall, owing to position is different, length is different, the heat absorbed is different, the temperature of water wall intraductal working medium can be caused different, cause water wall tube material temperature different. This kind of temperature difference, if do not controlled, can play thermal stresses drawing crack because of temperature contrast, destroy water wall pipe when severe.
Conventional overcritical pulverized coal firing boiler water wall generally adopts the water wall structure of " spiral pipe ", reduce the circulation area of water wall tube, improve the mass velocity of water wall intraductal working medium, spiral pipe is successively through the different positions of water wall simultaneously, evenly heat absorption, solves the problem of water wall safety as far as possible. The mass velocity of ultra supercritical pulverized coal firing boiler water wall is generally greater than 1000kg/m2.s��
Circular fluid bed, because having a large amount of recycle stocks in burner hearth, has a large amount of subsides wall katabatic drainage materials near water wall wall face. Spiral pipe structure water wall by subsides wall katabatic drainage heavy wear, thus cannot can adopt on circular fluid bed.
For these reasons, supercritical circulating fluidized bed boiler water wall adopts vertical tube to arrange, the mass velocity of water wall is general lower, is generally less than 1000kg/m2.s, it is called as " vertical tube low-quality flow ". The water screen system of low-quality flow utilizes " the self compensation characteristic " of working medium to distribute the flow of water wall so that the strong pipe that absorbs heat is assigned to many flows, strengthens pipe cooling, reduces pipe surface temperature.
But, inventor herein but finds under study for action, the overcritical CFB boiler water wall of low-quality flow is adopted to there is a difficult problem for more serious underload current downflow stability difference: boiler is when underrun, owing to the flow of water wall reduces, working medium (water or steam in water wall pipe, or both mixtures) flow stability decline, it is being disturbed, such as indirect heating strengthens, or flow reduces, easily occur that Working fluid flow speed sharply changes, water is by heating and gasifying, further block water cold wall pipe of the steam produced, cause flow to reduce, formed bear to feedback, the final pipe surface temperature that causes raises.
Therefore low-quality flow the design of overcritical CFB boiler water wall need the stability problem managing to solve the flowing when underload, prevent from bearing and occur to feedback. But, when how to realize low-quality flow, the overcritical CFB boiler water wall design of high stability of flow under completing underload, not relevant technology is open.
In addition, the overcritical CFB boiler water wall of low-quality flow adopts an one through boiler, and namely the working medium in water wall (water or water vapour) is once absorbed heat by water wall, is directly heated to form superheated vapour. This requires that heat absorption amount ratio (about 36-40%) of supercritical boiler water-cooling wall increases than subcritical water wall heat absorption ratio (being less than 29%), and water screen system must increase more area could meet requirement. If the height not taking innovative approach boiler water wall can increase very fast, cause the rising of boiler cost. In boiler hearth of circulating fluidized bed, heat exchange depends on the material of circulation in addition, and the recycle stock concentration that furnace height increases rear hearth top can reduce, and water wall heat exchange effect also can decline. Therefore to be managed to increase the area of supercritical circulating fluidized bed boiler water wall, but not cause furnace height to increase fast.
Solving in water wall area increase, there is water wall and the scheme of expansion screen series connection in prior art, the program increases screen formula extended surface in burner hearth, reduces furnace height, reduces boiler cost and manufacture difficulty. But the mass dryness fraction of the steam that water wall exports is had strict demand by this kind of series connection structure, such as " under boiler 30% load condition, working medium mass dryness fraction wants >=80% " " under boiler 50% load condition, working medium is heated to be saturation steam by water wall ". Above-mentioned requirements makes water wall still must have enough areas so that it is limited that furnace height reduces amplitude. In addition water wall and expansion screen series connection, water screen system mass velocity is very high, especially expands the mass velocity of screen. It is limited that mass velocity increases the temperature action to reducing tube wall, and the resistance of water wall also can be made to increase, and increases the energy consumption of boiler feedpump, reduces the economy of power plant.
Practical novel content
The purpose of this utility model: increase water wall area and furnace height problem under solving low-quality flow; Particularly, solve the overcritical CFB boiler water wall stability of flow decline problem at low load of low-quality flow, prevent water screen system from bearing and occur to feedback.
The object of this patent is realized by following technical proposals:
The overcritical CFB boiler water wall of high stability of flow under a kind of underload, comprise burner hearth surrounding water wall and the water-cooled mid-board of low-quality flow, and concentrated downtake and pipe connecting, the ips on the top of burner hearth surrounding water wall and water-cooled mid-board is greater than the internal diameter of bottom, Working fluid flow is in parallel at surrounding water wall and water-cooled mid-board, by concentrating, downtake causes surrounding water wall and water-cooled mid-board respectively in the feedwater of boiler, then causing by pipe connecting and converge header mixing, the steam converging header outlet causes the superheater in downstream.
The supercritical circulating fluidized bed water screen system of this patent comprises surrounding water wall and water-cooled mid-board. Although surrounding water wall and water-cooled mid-board this kind of parts boiler below little capacity, particularly subcritical parameter has had application. But the parameter of boiler reach overcritical after, natural circulation (or pump circulation) water screen system that drum-downtake-water wall that the following boiler of subcritical parameter adopts-drum is formed cannot adopt. The surrounding water wall of this patent and water-cooled mid-board Parallel Design increase water wall area and furnace height problem under solving low-quality flow. Owing to adopting low-quality flow design, (mass velocity is generally less than 1000kg/m simultaneously2.s, particularly 700��350kg/m2As previously mentioned .s), inventor herein finds, underload stability of flow problem specific to supercritical circulating fluidized bed boiler have occurred in surrounding water wall and water-cooled mid-board.
The conventional general lower inner diameter in supercritical water cold wall pipe footpath is big, and upper inner diameter is little. This is because, top working medium temperature height, it may also be useful to less internal diameter can improve the flow velocity of steam, strengthens the cooling power to tube wall, reduces pipe surface temperature. In addition, top caliber is little less than bottom, is the ability bearing interior pressure in order to increase pipe. Boiler design person is clear, and in identical pipe in pressure situation, caliber is more little, and required wall thickness is more little.
And the contriver of this patent finds under study for action: the supercritical circulating fluidized bed boiler of low-quality flow is different from conventional boiler, when solving stability problem, can not method routinely. Working medium (water, steam or steam water interface) in the pipe of surrounding water wall and water-cooled mid-board is heated in flow process, volumetric flow rate constantly increases along with by heating, for realizing " the self compensation characteristic " of low-quality flow, prevent water by heating and gasifying, further block water cold wall pipe of the steam produced, cause flow to reduce, formed bear to feedback, inventor herein need to change according to the specific volume of working medium on the top of surrounding water wall and water-cooled mid-board, increases the internal diameter of pipe. Namely formed: the ips on the top of burner hearth surrounding water wall and water-cooled mid-board is greater than the internal diameter of bottom. The definition of described upper and lower concept is that tube interior steam rates 50% is for decomposing line in upper and lower. The region of intraductal working medium phase transformation (becoming steam by water) should be avoided in the position of surrounding water wall, water-cooled mid-board pipe upper and lower caliber change, is namely greater than the position increase caliber of more than 50% at steam rates. And as preferably, the sectional area of top pipe is 1.05��3 times of lower tube sectional area.
As selection, do not have between surrounding water wall, water-cooled mid-board pipe upper and lower to mix or (with) device that distributes. The program can avoid mixing or (with) distribution device occurs working medium layering, water and steam distribution uneven.
As selection, water-cooled mid-board extends to top from burner hearth bottom. In the program, in order to increase water screen system heat interchanging area, exceeding increase boiler height simultaneously, cause cost to increase considerably, surrounding water wall disclosed in this patent and water-cooled mid-board have lot of advantages. The expansion screen of prior art, if being arranged in the top of burner hearth, after supercritical circulating fluidized bed boiler hearth height increases, upper furnace material concentration is lower, the heat transfer coefficient decline on top, and the heat exchange efficiency of expansion screen is lower, for reaching identical heat absorption amount, it is necessary to more material. The water-cooled mid-board of this patent extends to top from burner hearth bottom, and the middle lower disposed at burner hearth has water-cooled mid-board, coefficient of heat transfer height, it is possible to save material.
As selection, water-cooled mid-board be arranged in burner hearth exhanst gas outlet passage just to furnace wall cooling on, at connecting position, water-cooled mid-board and furnace wall cooling are welded together. In the program, water-cooled mid-board be arranged in burner hearth exhanst gas outlet passage just to furnace wall cooling on, be conducive to flue gas in burner hearth to flow in a organized way, prevent irregular eddy current, occur sweep of gases abrasion. Water-cooled mid-board and surrounding water wall are welded to connect, and are conducive to preventing the vibrations of water-cooled mid-board and distortion.
As selection, water-cooled mid-board is two-sided to be heated, and the ips of composition water-cooled mid-board is greater than the ips of composition burner hearth surrounding water wall. In the program, water-cooled mid-board is in burner hearth, and pipe heat absorption is strong, it is preferable that the caliber of scheme water-cooled mid-board be greater than the caliber of surrounding water wall.
As selection, the ips that burner hearth surrounding water wall is bent to form the part of exhanst gas outlet passage is greater than the internal diameter of other position pipes. In the program, having more bend pipe on surrounding water wall top, the region causing Working fluid flow resistance big, such as exhanst gas outlet etc., the ips in these regions is greater than the internal diameter of other position pipes.
As selection, water-cooled mid-board is heated length difference, pipe coating fire-resistant material heat absorption length is short on the top of water-cooled mid-board.
As selection, the width of water-cooled mid-board is no more than the half of furnace depth. The program does not affect flue gas in burner hearth and flows in a organized way.
As selection, water-cooled mid-board is arranged multiple, and each water-cooled mid-board is arranged symmetrically with on burner hearth section. In the program, it is the area increasing water screen system, it is possible to multiple water-cooled mid-board is arranged in the burner hearth that surrounding water wall is formed, and during the multiple layout of water-cooled mid-board, should be arranged symmetrically in burner hearth, be conducive to fire box temperature even.
As selection, the burner hearth both sides of boiler are all furnished with exhanst gas outlet passage, and multiple water-cooled mid-board is arranged between the exhanst gas outlet passage of both sides and the face that is arranged in a row, and leaves exhaust gases passes between each water-cooled mid-board.
The main scheme of aforementioned the utility model and each further selection scheme thereof can independent assortment to form multiple scheme; it is the utility model can adopt and claimed scheme: such as the utility model; each selection can select arbitrary combination with other; those skilled in the art can understand there is multiple combination according to prior art and common practise after understanding the utility model scheme; it is the claimed technical scheme of the utility model, does not do exhaustive at this.
The beneficial effects of the utility model: increase water wall area and furnace height problem under solving low-quality flow; Particularly, solve the overcritical CFB boiler water wall stability of flow decline problem at low load of low-quality flow, prevent water screen system from bearing and occur to feedback.
Accompanying drawing explanation
Fig. 1 is the structural representation of the utility model embodiment;
Fig. 2 is the stove both sides of boiler water-cooled mid-board arrangement schematic diagram when arranging burner hearth exhanst gas outlet passage;
In figure, 1 is burner hearth, and 2 is tripping device, and 3 is economizer, and 5 is back-end ductwork, and 6 is feeding back device, and 8 is water wall, and 11 is surrounding water wall, and 14 for converging header, and 16 for concentrating downtake, and 17 is water-cooled mid-board, and 18 is exhanst gas outlet passage, and 21 is superheater.
Embodiment
Below in conjunction with specific embodiments and the drawings, the utility model is further described.
Shown in figure 1, a kind of supercritical steam cycle boiler water-cooling wall system, (best range of mass flow is 700��350kg/m to comprise low-quality flow2.s) burner hearth surrounding water wall 11 and water-cooled mid-board 17, the feedwater of boiler is caused parallel burner hearth surrounding water wall 11 and water-cooled mid-board 17 by concentrated downtake. Working medium is heated in surrounding water wall 11 and water-cooled mid-board 17, causes convergence header 14 to mix by pipe connecting. Under supercritical behavior, the steam converging header 14 outlet is directed to the superheater 21 in downstream. In order to meet supercritical circulating fluidized bed boiler safety when underrun, prevent pressure surge and flowing instability that in burner hearth surrounding water wall 11 and water-cooled mid-board 17, working medium heat absorption is expanded and caused, it is greater than the internal diameter of bottom at the ips of composition burner hearth surrounding water wall 11 and water-cooled mid-board 17 top. Namely the position increase caliber of more than 50% it is greater than at steam rates. And as preferably, the sectional area of top pipe is 1.05��3 times of lower tube sectional area.
Water-cooled mid-board 17 be arranged in burner hearth exhanst gas outlet passage 18 just to furnace wall cooling 11 on, at connecting position, water-cooled mid-board 17 and surrounding water wall 11 are welded together. This kind of connection can prevent water-cooled mid-board 17 from shaking. When water-cooled mid-board 17 is two-sided being heated, namely water-cooled mid-board 17 is placed in burner hearth, and both sides are not all connected and fixed with surrounding water wall 11, and the ips now forming water-cooled mid-board 17 is greater than the ips of composition burner hearth surrounding water wall 11.
The ips that surrounding water wall 11 is bent to form the part of exhanst gas outlet passage 18 is greater than the internal diameter of other position pipes.
Water-cooled mid-board 17 be heated length different time, pipe coating fire-resistant material heat absorption length is short on the top of water-cooled mid-board 17, stagnates, to prevent underload is working medium, cause overheated.
In order to reduce water-cooled mid-board 17 to the impact of flow of flue gas in burner hearth, the width dimensions B of water-cooled mid-board 17 should be no more than 0.5A, is namely no more than the half of furnace depth. When water-cooled mid-board 17 is arranged multiple, should be arranged symmetrically with on burner hearth section, namely along the symmetrical arrangement in side wall direction, burner hearth left and right or along symmetric offset spread before and after front-back wall direction.
Another embodiment, when burner hearth exhanst gas outlet passage 18 (burner hearth exhanst gas outlet passage 18 is all arranged in the left and right sides such as accompanying drawing 2) when burner hearth is all arranged in the stove both sides of boiler, multiple water-cooled mid-board 17 is arranged between both sides exhanst gas outlet passage 18 to be arranged in a row face. In this case, water-cooled mid-board more than 17 is arranged, should leave exhaust gases passes between each water-cooled mid-board 17, the flue gas pressures of balance burner hearth.
The foregoing is only better embodiment of the present utility model; not in order to limit the utility model; all any amendment, equivalent replacement and improvement etc. done within spirit of the present utility model and principle, all should be included within protection domain of the present utility model.
Claims (8)
1. the supercritical circulating fluidized bed boiler water wall of high stability of flow under a underload, comprise burner hearth surrounding water wall and the water-cooled mid-board of low-quality flow, and concentrated downtake and pipe connecting, it is characterized in that: the ips on the top of burner hearth surrounding water wall and water-cooled mid-board is greater than the internal diameter of bottom, Working fluid flow is in parallel at surrounding water wall and water-cooled mid-board, by concentrating, downtake causes surrounding water wall and water-cooled mid-board respectively in the feedwater of boiler, then cause by pipe connecting and converge header mixing, the steam converging header outlet causes the superheater in downstream.
2. the supercritical circulating fluidized bed boiler water wall of high stability of flow under underload as claimed in claim 1, it is characterized in that: water-cooled mid-board be arranged in burner hearth exhanst gas outlet passage just to furnace wall cooling on, at connecting position, water-cooled mid-board and furnace wall cooling are welded together.
3. the supercritical circulating fluidized bed boiler water wall of high stability of flow under underload as claimed in claim 1, it is characterised in that: water-cooled mid-board is two-sided to be heated, and the ips of composition water-cooled mid-board is greater than the ips of composition burner hearth surrounding water wall.
4. the supercritical circulating fluidized bed boiler water wall of high stability of flow under underload as claimed in claim 1, it is characterised in that: the ips that burner hearth surrounding water wall is bent to form the part of exhanst gas outlet passage is greater than the internal diameter of other position pipes.
5. the supercritical circulating fluidized bed boiler water wall of high stability of flow under underload as claimed in claim 1, it is characterised in that: water-cooled mid-board is heated length difference, pipe coating fire-resistant material heat absorption length is short on the top of water-cooled mid-board.
6. the supercritical circulating fluidized bed boiler water wall of high stability of flow under underload as claimed in claim 1, it is characterised in that: the width of water-cooled mid-board is no more than the half of furnace depth.
7. the supercritical circulating fluidized bed boiler water wall of high stability of flow under underload as claimed in claim 1, it is characterised in that: water-cooled mid-board is arranged multiple, and each water-cooled mid-board is arranged symmetrically with on burner hearth section.
8. the supercritical circulating fluidized bed boiler water wall of high stability of flow under underload as claimed in claim 1, it is characterized in that: the burner hearth both sides of boiler are all furnished with exhanst gas outlet passage, multiple water-cooled mid-board is arranged between the exhanst gas outlet passage of both sides and the face that is arranged in a row, and leaves exhaust gases passes between each water-cooled mid-board.
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN106224945A (en) * | 2016-08-30 | 2016-12-14 | 华电电力科学研究院 | Supercritical circulating fluidized bed boiler hearth square waveform mid-board |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN106224945A (en) * | 2016-08-30 | 2016-12-14 | 华电电力科学研究院 | Supercritical circulating fluidized bed boiler hearth square waveform mid-board |
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