Keep secondary wind speed stable combustion technology during boiler at low load
Technical field patent of the present invention belongs to the electricity generation boiler Engineering Speciality, is used for the thermal power plant and adopts DC burner (four jiaos and the polygonal layout) smooth combustion of boiler when underrun.
Background technology is influenced by peak load regulation network and other reason owing to power plant, and boiler must move under the little load condition of being everlasting.Boiler when little load operation since fire box temperature reduce, good aerodynamic field when not having oepration at full load again, secondary wind speed reduces a lot, and burner outlet thermal flue gas back flow reduces, and makes the coal powder ignition time delay, because disturbance reduces between the reduction of secondary wind speed and the wind, whole air-flow rigidity also weakens, and moves instability on the flame kernel, cause the boiler combustion shakiness, even catch fire.The main cause that causes boiler unstable combustion when underload is the minimizing in air output, and secondary wind speed is reduced, and reduced stiffness influences the formation of normal tangential firing in the stove.Changeable in order to improve the coal that the coal-burning power plant faces, a lot of steady combustion ways have appearred in the adaptive capacity that ature of coal descends and guarantee the steady combustion of boiler when underload at home and abroad in succession, as: precombustion chamber class burner; Bluff body class burner; Coal powder burner; Various forms of burners such as high speed difference type burner and W, U type flame boiler have all played certain steady combustion effect when boiler at low load moves.Existing various smooth burning method all is to work hard from a wind basically, has ignored the secondary wind action, has only solved the stable combustion problem of burner outlet, can not make all to reach good combustion efficiency in the whole burner hearth.Solve the angle that the reverse steady combustion of the primary and secondary air Concentric Counter-tangential of stable combustion problem system just changes overfiren air port from secondary wind aspect.
Summary of the invention the present invention is going into the stokehold to the original every layer of every angle secondary wind of boiler (not comprising surrounding air and sandwich wind) with dividing plate separated into two parts or directly be divided into two air channels and send in the stove in overfire air port, it is original per share secondary air separating two strands promptly, wherein one installs plate washer (claiming controlled secondary wind plate washer later on) in addition additional, and another thigh is not adorned plate washer.When boiler load reduces since air output reduce, blast and secondary wind speed all can reduce, can control into the total secondary air flow of stove by suitably turning down the controlled secondary wind plate washer that installs additional, owing to send into reducing of the interior main flow secondary wind discharge area of stove, the air-supply blast is kept to be changed not quite, another strand secondary wind outlet wind speed changes also little substantially, makes into unlikely the weakening of stove secondary wind integral rigidity, can keep the formation of stove inscribed circle burning.Though stove internal cause load reduces and the corresponding reduction of temperature, because of other condition changes not quite, the burning meeting of fuel is still stable in the stove.The mode of overfiren air port internal partition installing should be according to the residing determining positions of each overfiren air port, the ratio that each overfiren air port air quantity is cut apart should be fixed according to the zone and the boiler minimum load retention value at overfiren air port place, and the secondary wind air quantity ration of division at every layer of each angle should be consistent.The present invention compares with existing stable combustion technology, mode, method difference, when any load, do not change original combustion system, have simple in structurely, surely fire effective, small investment, maintenance cost is low, the combustion efficiency in the time of can reaching at full capacity during underload basically.Help peak regulation and reduce boiler oil consumption and over-emitting black exhaust during ignition start, over-emitting black exhaust and saving help fuel oil when reducing boiler at low load.Can accomplish reasonable actual air volume during boiler at low load, improve boiler thermal output.
The dividing method of description of drawings air quantity has a variety of, and the dividing method that has is also difficult with graph expression, can not enumerate one by one, here be square and two kinds of situations of rectangle (L/S=1.25) with regard to the boiler furnace horizontal section, adopting dividing plate to carry out vertical segmentation with overfiren air port is the wherein dividing method of one deck (secondary wind direction of rotation serves as counterclockwise) of example description of drawings.Fig. 1 is the wherein schematic diagram of one deck overfiren air port air quantity vertical segmentation of square boiler for the burner hearth horizontal section, and Fig. 2 is the wherein schematic diagram of one deck overfiren air port air quantity vertical segmentation of the rectangular boiler of burner hearth horizontal section, and overfiren air port is square or rectangle.Because of overfiren air port part as according to the words that actual ratio the is drawn practical structures that is beyond expression, handle so do to amplify.Because of inaccuracy such as particular size and secondary wind exit angle in the horizontal finite graph that charts.
Specific embodiment the present invention adopts dividing plate to cut apart that air quantity is more to be established the air channel to cut apart air quantity simple when implementing, it is the simplest and be convenient to control and adjust that the air quantity of each overfiren air port is divided into two parts, cuts apart simpler for the employing of square and rectangle is horizontal or vertical to overfire air port.Should the employing level cut apart when following secondary air separating is cut, controlled secondary wind plate washer is contained in lower part wind side, so that secondary wind is held coal dust.Attention should be contained in the little side of angle between secondary wind center line of discharge and the both sides furnace wall to controlled secondary wind plate washer when secondary air flow is carried out vertical segmentation, high speed secondary wind makes air-flow paste wall in the little side of angle when preventing underload.Dividing plate should be apart from secondary wind pelvic outlet plane indentation 50 millimeter, and preventing that the dividing plate outlet side from crumpling influences combustion efficiency, be difficult at the prerequisite lower clapboard that does not influence the installing plate washer long, the ventilation in the time of should not influencing normal duty.The vertical dividing plate of placing is parallel with two side walls, and vertical with last lower wall surface, the dividing plate of horizontal positioned is vertical with two side walls, and is parallel with last lower wall surface.Require to keep the load of steady combustion low more, controllable secondary wind total amount ratio is just big more, but should be taken into account the control difficulty of boiler least restrictive steam temperature when design minimum steady combustion load.Little to doing the boiler that side secondary air arranges because of the overfiren air port sectional area, adopt the way of control secondary wind speed to determine according to actual conditions.
When boiler during in rated load or near rated load operation, controlled secondary wind plate washer standard-sized sheet, dividing plate both sides secondary wind speed is basic identical, forms one air-flow in the exit, can adjust controlled secondary wind plate washer between the comparatively stable loading zone of stove internal combustion.When load variations need be done air quantity and adjusts, can normally adjust by former method, in order to strengthen stove internal combustion effect, also can increase whole secondary wind wind speed at the stove internal combustion suitable controlled secondary wind of control section plate washer under the stable case comparatively.Boiler should the bottom-up controlled secondary wind of each layer plate washer that suitably turns down when underrun, should be able to simultaneously operating with each angle of layer controlled secondary wind plate washer, and consistent to guarantee that each angle air quantity, wind speed change.Controlled secondary wind plate washer is not answered complete shut-down, should leave small part air quantity cooled nozzle and prevent accumulated powder in the spout, inconvenient as adjustment in service, controlled secondary plate washer operating system can be done spacing processing, or can control perforate on the secondary wind plate washer, even controlled secondary wind plate washer complete shut-down also has a small amount of wind to pass through.When 75% below when operation of boiler in rated load, what burner was furnished with sandwich wind and surrounding air should suitably control the amount of sending into, because the restriction of controlled secondary wind plate washer during underload, level when making the air-supply blast still maintain high load capacity, the amount of sending into of sandwich wind and surrounding air and wind speed will remain unchanged, and because load reduces and sends into coal dust amount minimizing in the stove, one time wind band powder concentration reduces, and it is unfavorable to coal powder ignition that sandwich wind and surrounding air are too much sent in the stove.When boiler load reduces or increasing degree when big, should note air quantity, the adjustment of wind speed and the maintenance of combustion chamber draft should not change excessive.Boiler is when underload, and what the air-supply blast kept should be not too high and low excessively, is unlikely to too high and low excessively to guarantee whole secondary wind speed, rationally control secondary wind speed, prevents burner outlet coking and scaling loss burner.
Adopt the boiler of the steady combustion of the present invention should do the minimum load stability test, so that grasp different coal minimum load stationary values, reference during for peak regulation and band minimum load.
