本科毕业设计外文文献及译文定稿.doc

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1、本科毕业论文外文文献及译文文献、资料题目：Influence of Coal-feed Rates on Bituminous Coal Ignition in A Full-scaleTiny-oil Ignition Burner文献、资料来源：期 刊文献、资料发表（出版）日期：2009.8.5院 （部）： 热能工程学院专 业： 热能与动力工程班 级： 热动073姓 名： 仲明凯学 号： 指导教师： 杨冬翻译日期： 2011.3.31外文文献Influence of Coal-feed Rates on Bituminous Coal Ignition in A Full-scaleTin

2、y-oil Ignition BurnerA B S T RACTA tiny-oil ignition burner has been proposed to reduce oil consumption during the firing-up process and partial-load operations. To investigate the influence of different feed rates on bituminous coal ignition in the tiny-oil ignition burner, full-scale reacting-flow

3、 experiments were performed on an experimental setup.The ignition burner was identical to that normally used in an 800-MWe utility boiler. Gas temperature distributions in the burner were obtained at coal-feed rates of 2, 3, 4, and 5 tonnes/h. Char burnout and release of C and H were observed at the

4、 exit of the burner nozzle. Gas compositions such as O2 and CO were measured in the center of the burner. A change in resistance was obtained within the burner. A saving of 90% over previous oil consumption was gained in the firing-up process by using the new oil-gun technology.Key words: Tiny-oil i

5、gnition burner ；Coal-burning utility boiler；Coal-feed rates1. IntroductionTo fire-up a boiler, oil is primarily used to pre-heat the combustion chamber of a furnace bringing it to its operating temperature.Generally, oil is delivered under high pressure by an oil-gun with a delivery capacity of abou

6、t 1 tonne/h. Therefore, in the initial firingup process of a bituminous coal-fired 300 MWe utility boiler, about 100 tonnes of fuel oil would be consumed. Concerns over increasing economic costs in pulverized coal-fired power stations arising from oil consumed in the firing-up process and partial-lo

7、ad operations has spurred interest in developing oil-free and tiny-oil ignition burners. Various investigators have reported studies of oil-free ignition burners. Masaya et al. studied the stabilization of pulverized coal combustion using a plasma-assisted burner, while Kanilo et al. investigated th

8、e ignition and combustion of pulverized coal using a microwave-assisted burner. In China, Zhang et al. described their application of plasma ignition technology in bituminous coal-fired boilers. However, for such burners, two main problems arise: difficulties in extending the capacity of the burner

9、and the frequent maintenance required during operation. Li et al. investigated induction-heating ignition of a pulverized coal stream. Induction-heating can supply a reliable convenient source of energy to ignite the pulverized coal stream, but this technology has not been previously reported to hav

10、e been used in any utility boiler.An alternative tiny-oil ignition burner has been developed and tiny-oil ignition, centrally fuel-rich burners proposed (see Fig. 1). The burner features two oil-guns arranged in the central pipe and the firing-up process is summarized as follows. Atomized oil from o

11、ne oil-gun, called the main oil-gun, ignites and burns in an adiabatic chamber. Subsequently, an oil flame ignites the atomized oil from the other oil-gun, called the auxiliary oil-gun. Cone separators are installed in the primary aircoal mixture duct to concentrate the pulverized coal into the cent

12、ral zone of the burner. The fuel-rich primary aircoal mixture passes into the first combustion chamber whereby the fuel-rich primary aircoal mixture is ignited by a high-temperature oil flame formed by both main and auxiliary oil-guns. Next, the burning pulverized coal and oil flame from the first c

13、ombustion chamber is directed into the second combustion chamber where the coal is ignited. After the boiler has been fired-up, both main and auxiliary oil-guns are then shut down and the burner switches operations to becoming a centrally fuelrich burner . Characterized by high combustion efficiency

14、 and low NOx emission. The influence of coal-feed rates on the bituminous coal ignition in the full-scale tiny-oil ignition burner was investigated.2. Experimental set-upFig. 1 shows the tiny-oil ignition apparatus. The ignition burner was identical to the burner that had been used in an 800-MWe uti

15、lity boiler and its operation is briefly described as follows. The feeder supplies pulverized coal by primary air from the blower. The pulverized coal is then carried to the tiny-oil ignition burner by primary air. Oil is drawn from the oil tank and sent to the main and auxiliary oil-guns atomizing

16、the oil mechanically and by air. Although compressed air enters the oil-guns, a small fraction is also consumed in oil combustion, the main body of which is supplied by another blower. The pulverized coal is ignited in the primary air duct. In the experimental set-up there was no separation into inn

17、er and outer secondary air.All gas temperatures were measured at the center of the burner as well as the exits of the first and the second combustion chambers. Ash samples were sampled at the exit of the tiny-oil ignition burner. Gases were sampled using a water-cooled stainless steel probe and anal

18、yzed online on a Testo 350M instrument 5. The probe, consisting primarily of a water-inlet pipe, water-outlet pipe, sampling tube, outer pipe and supporting components, was bracket-mountedat the exit of the burner. A sample of the high-temperature gas is collected in the sampling tube and cooled by

19、high pressure cool water delivered through the water-inlet pipe cooling the sampling tube and after heat change flows out via the water-outlet pipe. A water pump provided continuous water circulation. When gas enters the sampling tube, temperatures decease rapidly and the pulverized coal stops burni

20、ng. Samples are drawn up by a pump through filtrating devices into a Testo 350M gas analyzer for subsequent analysis. The accuracy of the analyzer for each species measurement is 1% for O2 and 5% for CO. Each sensor was calibrated before measurement. COmax is 10,000 ppm in this experiment.The differ

21、ence in pressure before and after ignition is called the burner resistance. A static pressure method was used to measure ignition resistance at the position of the straight section (See Fig. 1). One end of the u-tube differential manometer was connected with a static pressure hole, and the other end

22、 was open to atmospheric conditions.Table 1 lists equipment used along with their technical characteristics. Table 2 lists operating parameters. Table 3 lists the final analysis and other characteristics of 0 # light diesel oil used inthe experiments. Table 4 records the characteristics of the bitum

23、inous pulverized coal used in the experiments. The methods used to measure calorific value, proximate analysis and ultimate analysis were in accordance with 213-2003, 212-2001 and 476-2001 of the Chinese standards code, respectively. The pulverized coal fineness was R90 = 9.2%, i.e. 90.8% of all par

24、ticles pass through a 90 lm aperture sieve.3. Result and discussion3.1. The gas temperature distributionFig. 2 depicts gas temperature profiles measured along the burner center line; here x is the measured distance from the central pipe exit (See Fig. 1). Using the two oil-guns in the absence of coa

25、l during firing-up, gas temperatures decreased from 1044 _C to 856 _C with increasing distance. Most of the oil from both main and auxiliary oil-guns burnt out in the central pipe. High-temperature gas was then formed. As the gas flowed toward the burner nozzle, cold air diffuses into it resulting i

26、n a gradual decrease in gas temperatures. Using the two oil-guns in the presence of coal during firing-up, the high-temperature oil flame ignited the pulverized coal releasing heat as it continuously burned. As a consequence, gas temperatures increased along the direction of the primary air flow, i.

27、e. along the burner center line.Fig. 3 shows the gas temperature profile measured at the exits of the first and second combustion chambers, at a radius of r1 and r2, respectively, from the center line of the burner (See Fig. 1). During firing-up with the two oil-guns operating in theabsence and then

28、 later in the presence of coal, gas temperatures were observed to be largest along the center line. As the radius increased, gas temperatures decreased gradually. Wall temperatures of the first and the second combustion chambers were less than 116 _C and 127 _C, respectively. At low temperatures, th

29、e burner wall was safe.During firing-up with the two oil-guns operating in the absence of coal, gas temperature distributions were similar at the exits of the first and the second combustion chamber. The oil-flow rate of auxiliary and main oil-guns was 65 and 35 kg/h, respectively (See Table 2). The

30、 oil-flow rate of auxiliary oil-gun was higher than that main oil-gun. The released heat on the side of the auxiliary oilgun (r1 0 and r2 0 and r2 0). Hence gas temperatures on the side of the auxiliary oil-gun were higher than those on the side of themain oil-gun. For example, at the first combusti

31、on chamber exit, gas te eratures at r1 = _57 and _114 mm, where the auxiliary oil-gun was mounted, were 1005 _C and 767 _C, respectively, and at r1 = 57 and 114 mm, where the main oil-gun was mounted, were 601 _C and 203 _C, respectively. Gas temperatures at the second combustion chamber exit are lo

32、wer than those at the first combustion chamber exit. Most of the oil of the main and auxiliary oilgunsburned out in the central pipe. As the gas flowed from the first combustion chamber to the second, it mixed with cold air, thus gradually decreasing gas temperatures.During firing-up with the two oi

33、l-guns in the presence of coal, the pulverized coal burned adequately releasing heat in the process. Gas temperatures at the second combustion chamber exitwere higher than those at the first combustion chamber exit. By increasing coal-feed rates, more heat was absorbed by the pulverized coal thereby

34、 decreasing its temperature. At the same time,much more coal ignited; the released heat of combustion thereby increased and in the process the temperature of the pulverized coal would then increase. When coal-feed rates increased from 2 to4 tonnes/h, the released heat of combustion is more than the

35、absorbed heat. Thus at equivalent measuring points at the exits of the first and second combustion chambers and on the burner center line (see Fig. 2) gas temperatures gradually increased. When the coal-feed rate was increased to 5 tonnes/h, the released heat from coal combustion was less than the a

36、bsorbed heat. Thus gas temperatures at equivalent points decreased. However, pulverized coal can be successfully ignited. Oil from the main oil-gun was ignited by a high-energy igniter and burnt in an adiabatic chamber. Subsequently, the oil flame formed by the main oil-gun ignited the atomized oil

37、from the auxiliary oil-gun. Afterward, the igniter was closed, and the oil flamewas maintained by the two oil-guns and burned steadily. During firing-up using the two oil-guns in the presence of coal, instantaneous ignition was achieved by the oil flame and a steady burn of the pulverized coal devel

38、oped. The flame formed by the two oil-guns and pulverized coal was bright and steady during the whole process. Fig. 4 shows photos of the oil and coal flame.3.2. Char burnout and release rate of C and H at the exit of the burnerFig. 5 shows the char burnout and release rate of C and H at the exit of

39、 the tiny-oil ignition burner. Char burnout was calculated using=1-（wk/wx）/(1-wk)where w is the coal burnout factor, wk is the ash weight fraction in the input coal, and wx is the ash weight fraction in the char sample.is the percentage release of components (C and H), which wascalculated by=1-(wix/

40、wik)(wk/wx)where wix is the weight percentage of the species of interest in the char sample and wik is the weight percentage of the species of interest in the input coal 6.The distributions of char burnout and release rates of C and H were similar at the different coal-feed rates. The char burnout a

41、nd the release rates of C and H were largest along the burner center; as the radius increased, they decreased with the increase of coal-feed rates. At the center of the burner (r2 = 0), char burnout and release rates of C and H decreased from 83%, 81%, 95% to 75%, 72%, 87% as coal-feed rates increas

42、ed from 2 to 5 tonnes/h.3.3. Gas compositions and the burner resistanceTable 5 lists gas compositions at the center of the burner exit as well as the burner resistance. For coal-feed rates of 2, 3, 4, 5 tonnes/ h, O2 concentrations were in the range 0.010.04% and CO concentrations were more than 10,

43、000 ppm. The O2 concentration at the center point of the burner exit was almost exhausted. When the primary air temperature and velocity were 15 _C and 23 m/s, respectively, with oil-flow rate at 100 kg/h, the burner resistance while the two oil-guns were in operation increased 190 Pa in the absence

44、 of coal and in the presence of coal were 500, 600, 600, 550 Pa for coal feeding rates of 2, 3, 4, 5 tonnes/h, respectively.3.4. Consumed oilUsing the tiny-oil ignition burner, total oil-flow rate decreased from 1000 to 100 kg/h, thus saving 90% of the oil usually consumed in the firing-up process.4

45、. Conclusion(1) When the primary temperature and velocity air were 15 _C and 23 m/s, respectively, ignition was successful with an oil-flow rate of 100 kg/h and the bituminous coal-feed rate was increased from 2 to 5 tonnes/h. Wall temperatures of the first and the second combustion chambers were le

46、ss than 116 _C and 127 _C, respectively. At the low temperature, the burner wall was safe. O2 concentrations at the exit of the burner were 0.010.04%. During firing-up, the burner resistance increased to 190 Pa with coal absent and to 500600 Pa with coal present. A saving of 90% of the oil normally

47、consumed in the firing-up process represents a significant economic benefit.(2) Temperatures along the center line of the burner gradually increased along the direction of the primary air flow in the presence of coal. As coal-feed rates increased from 2 to 4 tonnes/h, gas temperatures at equivalent

48、points at the exits of the first and second combustion chambers and on the center line increased gradually. A further increase of the coal-feed rate to 5 tonnes/h decreased temperatures at these points.(3) Distributions of char burnout and release rates of C and H were similar for different coal-feed rates; as the radius increased, they decreased with the increase of coal-feed rates. Finally, increasing coal-feed rates decreased char burnout and release rates of C and H at equivalent points at the exits. Acknowledgements This work was supported by the