PLASMA IGNITER WITH ASSEMBLED CATHODE |
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| 申请号 | EP02703472.7 | 申请日 | 2002-02-27 | 公开(公告)号 | EP1371905B1 | 公开(公告)日 | 2010-12-01 |
| 申请人 | Yantai Longyuan Power Technology Co. Ltd.; | 发明人 | WANG, Aisheng; TANG, Hong; JI, Shuxin; WANG, Yupeng; TIAN, Dong; WANG, Gonglin; REN, Weiwu; CHEN, Xueyuan; SHAO, Ruihu; ZHANG, Xiaoyong; MA, Shuang; | ||||
| 摘要 | This invention relates to a plasma igniter for directly igniting the coal-powder furnace. Said plasma igniter consists of a plasma generator which includes a composite anode, an assembled cathode, an electromagnetic coil and a transmitting coil; a coal powder burner which comprises mutt-stage pipes for conveying igniting coal, an equipment for adjusting thickness of coal powder and a four-stage burner canister; and a generator brace. Said assembled cathode consists of a cathode plate, a fixation nut, a conductive pipe, a inflooding pipe, a inflooding guiding pipe, a cathode lid and a sealing spacer. The lining for generatoring electric arc is assembled with the front of cathode. An alloy plate is used as the cathode plate. The nozzle that used for cooling the cathode is first convergent and then expansive, and is placed in the middle of the conductive pipe. The plasma igniter has the advantage of stableburning. It can be used as not only a main burner for the boiler but also a igniting burner. Since oil is not used, lots of petroleum source is saved. | ||||||
| 权利要求 | |||||||
| 说明书全文 | The present invention relates to a a plasma ignition device for directly igniting a pulverized coal burner. The plasma ignition device can use a cathode. The plasma ignition device is used for directly starting a pulverized coal boiler. The plasma ignition device is used in the starting ignition stage and the low-load stable combustion stage of the pulverized coal boiler, and may serve as the primary burner of the pulverized coal boiler as well. The starting ignition and low-load stable combustion of the conventional industrial pulverized coal boiler rely on burning oil. In the year of 1999, me pulverized coal boilers of the state power system of China consumed about 2.87 million tons of oil, amounting to about 10 billion RMB yuan in value. Since the 1980's, the technologists of different countries focused on developing technologies adopting plasma technology in directly igniting the pulverized coal. An Australian has developed a plasma ignition device, in which the electrodes are protected with nitrogen gas and fat coal is burned. The former Soviet Union has made a large amount of fundamental research and made experiments in power plants in Baoji and Shaoguan in China respectively in 1996 and 1998, but the experiments were not successful. The Tsinghua University and Harerbin Boiler Factory in China have also made a large amount of research. Various plasma ignition devices for directly igniting pulverized coal developed in different countries failed to achieve progress in some important technical problems such as ensuring the continuous operation of the generator and preventing the burner from coking, thus have not been adopted widely. A patent of utility model of the applicant, no. For overcoming said shortcomings, the applicant filed and was granted a patent for utility mode no. The European Patent Application No. The U.S. Patent The International Patent Application No. The European Patent Application The object of the invention is to provide a plasma ignition device for directly igniting a pulverized coal burner, in which the plasma generator can operate continuously and stably, while ensuring that the pulverized coal burner is not easily subject to coking or burning loss, thus operates reliably. Above object is realized by a plasma ignition device in accordance with the features of claim 1, for directly starting a pulverized coal boiler. Said plasma ignition device can comprise a plasma generator, pulverized coal burner and dc power supply, wherein said plasma generator comprises combined type cathode, composite anode, electromagnetic coil, arc-starting coil mounted surrounding the housing of the composite anode, and linear motor, and said pulverized coal burner can comprise burner nozzle, four stages of burning chambers, powder-air tubes, primary air-powder tube, guide plates, high-temperature plasma transporting pipe and powder-concentration-adjusting guide plate. An additional object of the invention could be to provide a combined type cathode used in plasma ignition device. A combined type cathode used in a plasma ignition device, can comprise cathode head, tight nuts, electrically conductive tube, water inlet tube, water inlet pipe, water outlet tube, cathode end cap and sealing cushion, said cathode head is welded to the tight nuts of copper, said electrically conductive, tube is jointed to the nuts by screwed connection, a water inlet tube is inserted into the other end of the electrically conductive tube, and is jointed thereto by welding or screwed connection, a water outlet tube is mounted by welding in the direction perpendicular to the electrically conductive tube, thereby a cooling system of the cathode is formed, characterized in that on the front end of the cathode is mounted a dedicated arc-starting bush, the cathode plate is made of alloy plate, and a cooling nozzle is adopted. Said cooling nozzle is constructed so that it is first convergent and then divergent. Under normal operation condition, the inventive combined type cathode has the following properties:, self-contracting electric arc, stable voltage, long cycle-life, few burning loss of the anode during arc starting, considerably reduced cost. Therefore, the reliability of the plasma ignition device is improved. According to a preferred embodiment of the invention, said composite anode is in form of double nozzle tubes. Said anode body is made of material having high thermal conductivity and high electrical conductivity and the oxide of which is also electrically conductive, preferably Ag-based alloy, and the anode nozzle may be made of Ag-based alloy or red copper. Said combined type cathode comprises cathode head, arc-starting bush, tight nuts, cathode plate, cooling nozzle, electrically conductive tube, water inlet tube, water inlet pipe, water outlet tube , electrically conductive tube and cathode end cap. Said cathode plate is in shape of a cylinder plus a cone, and is attached to the cathode head through welding, and is made of Ag-based material, the cooling nozzle is constructed so that it is convergent first and then divergent. Since the combined type cathode adopts high-velocity nozzle with forced cooling, the heat transmission of the cathode is accelerated and the life of the cathode is lengthened. The life of the cathode is further improved through adopting good electrically conductive and good thermally conductive material, preferably Ag-based material as cathode plate. Through adopting the composite anode, the flow field of the plasma in the inner cavity of the anode is changed In particular, at the nozzle, the axial component of the flow is dominant, and thus the anode is prevented from being contaminated by the pulverized coal. In addition, since the receiving area of the anode is increased on the basis of the conventional nozzle, the electrons are received within the anode nozzle tube, and thus will not be disturbed by any external dynamic field, and thus the output power of the equipment is very stable. The are-transporting coil coated outside of the composite anode increases the length of the plasma flame, and thus improve the ability of igniting the pulverized coal. Furthermore, adopting multi-stage axial powder delivery and gas film cooling techniques, and performing ignition through stage-by-stage amplification, which increase greatly the output power of the burner with lower power consumption, the burner has functions of ignition and stable combustion, as well as serving as primary burner. Specifically, auxiliary air is adopted to perform air film cooling of the first, second, third and fourth burning chambers, so that the wall temperature of the burning chambers is decreased below the ash fusion temperature and coking is prevented. In the third stage burning chamber, the oxygen is supplemented by the low concentration powder flow; in the fourth burning chamber, the oxygen is supplemented by the auxiliary air, so that the burning is enhanced and the rigidity of the flame is improved. Therefore, the inventive plasma ignition device has advantages of great power, no coking, high burning efficiency, strong rigidity of flame, and various coals can be burned therein. Since the inventive equipment solves the key techniques relating to the continuous and stable operation of high power plasma ignition device, the inventive plasma ignition device may be widely applied in industrial pulverized coal boiler. The conventional method of starting and igniting industrial boiler and making it stably operating with oil will be replaced, and a large amount of petroleum will be saved. The preferred embodiments of the present invention will be discussed in details with reference to the accompanying drawings, in which,
Now the preferred embodiment of the present invention will be described in details with reference to the accompanying drawings. First all the reference signs in the figures will be described in the following table. As shown in According to a preferred embodiment, the are-starting bush 311 is made of graphite rod, which has high fusion temperature and high electrical conductivity, the arc-starting bush 311 is fastened on the front end of the cathode head 301 through screwed connection, and is flush with the cathode plate 302. According to another preferred embodiment, the cathode plate 302 is made of Ag-based alloy plate, which has high thermal conductivity and high electrical conductivity, the cathode plate 302 is jointed to the cathode head 301 through brazing, and is flush with the arc-starting bush 311. Adopting plate-type cathode enables the self-contracting of the arc starting point. During the operation of the plasma ignition device adopting above combined type cathode, as shown in In addition, since the cooling nozzle of the cooling system of the cathode adopts a nozzle tube has a structure that is first convergent and then divergent, the liquid is accelerated in the throat portion of the nozzle, so that the efficiency of the heat exchange of the cathode is improved and the life of the cathode is lengthened. As shown in Through flange connection, the plasma generator 102 has its composite anode 604 inserted into the first stage burning chamber 212 of the pulverized coal burner. As shown in As shown in As shown in As shown in The principle and the operation of the invention will be described below with reference to At the same time, the pulverized coal introduced by the primary air-powder tube 217 is divided by the coal-concentration-adjusting guide plate into three streams, which enters into the burner body. A first portion of 20% of the high concentration pulverized coal enters into the first stage burning chamber through the inlet tube 215 of the first stage burning chamber and the guide plate of the first stage burning chamber, and is ignited by said plasma flambeau. The second stream, 60% of the high concentration pulverized coal enters into the second stage burning chamber through the inlet tube 216 of the second stage burning chamber and the guide plate of the second stage burning chamber. The third stream, 20% of the high concentration pulverized coal enters into the third stage burning chamber through the primary air-powder guide plate and the powder channel for the third stage burning chamber. Wherein, the auxiliary air passes through the auxiliary air inlet tube of the powder-air tube and enters into the burner by two ways. The air of one way passes through the upper inlet of the external cylinder of the first stage burning chamber to cool the outer wall of the first stage burning chamber, and then supplements oxygen for burning. The air of the other way passes through the auxiliary air channel to cool the outer wall of the third stage burning chamber, and then is further divided into two streams, one of which enters into the fourth stage burning chamber to supplement oxygen for burning, the other of which passes through the auxiliary air channel to cool the fourth stage burning chamber, then enters into the burner hearth. Thus, when the high-temperature plasma transporting tube provides a high-temperature plasma, as described above, the first portion of 20% of the high concentration pulverized coal is ignited immediately, the flame thereof further ignites the second portion of 60% of the pulverized coal, the rest 20% of the pulverized coal passes though the pulverized coal channel of the third stage burning chamber and mixes with above said flambeau and burns. The last portion of the powder-air flow also serves to cool the second stage burning chamber. Experiments show that when the amount of pulverized coal in the burning chambers is 500kg/h, the shape of the flame is ϕ700× 3000mm. The flame ignites the pulverized coal in the second stage burning chamber 206 and the third stage burning chamber 204. When the total amount of the pulverized coal is 5000kg/h, the temperature of the flame is greater than 1200 °C, the jetting velocity at the nozzle is about 45-55m/s, and the shape of the flame is approximately ϕ1000× 7000mm. When adopting four plasma ignition devices in straight-flow burner, tangential firing may be maintained, thus starting ignition and stable combustion may be realized. |
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