回轉(zhuǎn)窯內(nèi)移動(dòng)床溫度分布的測(cè)量和分析外文翻譯（英文）

1、Chemical Engineering and Processing 49 (2010) 147–150Contents lists available at ScienceDirectChemical Engineering and Processing: Process Intensificationjournal homepage: www.elsevier.com/locate/cepTemperature distribut

2、ion within the moving bed of rotary kilns: Measurement and analysisXiao Yan Liu a,?, Eckehard Specht ba College of Electrical and Information Engineering, Hunan University, Changsha 410082, Chinab Institute of Fluid Dyna

3、mics and Thermodynamics, Otto-von-Guericke-University Magdeburg, Universitaetsplatz 2, Magdeburg 39106, Germanya r t i c l e i n f oArticle history:Received 23 July 2009Received in revised form 2 December 2009Accepted 11

4、 January 2010Available online 20 January 2010Keywords:Rotary kilnTemperature measurementHeat transferGranularMoving beda b s t r a c tInadequacies in the temperature measurement within the moving bed have hindered a thor

5、oughunderstanding of the processes occurring within rotary kilns. A new measuring system, consisting ofthermocouple arrays, a radio-transmitter, a radio-receiver and a computer monitor is introduced in thispaper. With it

6、, the 3D temperatures within the moving bed, as well as the temperatures of the freeboardgas and the kiln wall, can be measured and saved automatically. Experiments with sand on a co-currentpilot kiln demonstrated that,

7、in the passive layer of the moving bed, the temperatures were approximatelyconstant in the circumferential direction. In the radial direction, however, large temperature differencewas observed within the bed near the fee

8、d end of the kiln, and the difference became smaller as the bedwent progressed through the kiln. This temperature measuring system can be used to obtain data overa wide range of operating conditions for use in engineerin

9、g design. The obtained results may give newthoughts in theoretical modeling of heat transfer within the moving bed of rotary kilns.© 2010 Elsevier B.V. All rights reserved.1. IntroductionRotary kilns are chemical re

10、actors widely used in the metallur-gical and chemical industries to handle bulk materials. The materialto be treated is fed into a cylindrical pipe and transported forwardsdue to the rotation and inclination of the pipe.

11、 During the trans-port process, the material exchanges heat with the energy carrier(combustion gas for example), being dried or calcinated. Despiteresearch efforts, the heat transfer process within the material bedhas no

12、t been well understood [1]. One of the reasons is the lack ofexperimental data needed to test the heat transfer models. Manyfactors, for example, the continuously rotating parts of the kiln andthe moving bed, make the te

13、mperature measurement within thematerial bed rather difficult. There are a few experimental studiesreported in the literature [2–4]. However, only the temperatures atthe bed surface or the temperatures near the kiln wall

14、 were mea-sured due to technical limitations. The temperatures at differentdepths of the bed were not investigated. In this paper, a new tem-perature measuring system using radio transmission technologyis described that

15、enables continuous temperature measurementwithin the moving bed in three dimensions, and the experimentalresults are discussed.? Corresponding author. Tel.: +86 731 88822224; fax: +86 731 85818386.E-mail address: xiaoyan

16、.liu@hnu.cn (X.Y. Liu).2. Experimental2.1. Experimental apparatus and measuring techniqueThe pilot kiln has a length of 6.7 m and an outer diameter of400 mm. The wall thickness is 75 mm, consisting of a 70 mm refrac-tory

17、 and a 5 mm steel shell (Fig. 1). The inclination of the kiln canbe varied from ?1? to +2? and the rotation speed of the kiln isadjustable in the range of 0–3.25 rpm. The kiln is fired on natu-ral gas using a programmabl

18、e burner with a maximal capacity of70 kW. The materials are fed into the kiln from a storage hopper,co-currently to the gas flow. In order to prevent overflow, a damwas installed at the feed end of the kiln.Along the kil

19、n length, four holes (‘measuring socket’) are drilledthrough the kiln shell (Fig. 1) to install thermocouples. In eachsocket, thermocouples are inserted into the kiln with differentradial distances to the center point of

20、 the kiln cross-section (Fig. 2),so that temperatures of the gas, the material bed and the kilnwall can be measured. Since the thermocouples rotate continu-ously together with the kiln, the thermocouples may stay in them

21、aterial bed and in the gas phase in one rotation. In order todetermine the circumferential position of the measuring point, apendulum is mounted on the kiln wall to measure the rotation angle? (? = 0–360?). In this way,

22、temperature profiles can be obtained asa function of the rotation angle at each axial position of the kiln,leading to a three-dimensional temperature measurement. Signalsfrom the thermocouples and the pendulum are routed

23、 to a sender0255-2701/$ – see front matter © 2010 Elsevier B.V. All rights reserved.doi:10.1016/j.cep.2010.01.008X.Y. Liu, E. Specht / Chemical Engineering and Processing 49 (2010) 147–150 149Fig. 3. Measured temper

24、ature profiles at the axial position z = 0.5 m.Fig. 4. Measured temperature profiles at the axial position z = 0.8 m.and ? = 270–360?). Figs. 3–6 illustrate the temperature profilesmeasured at the four axial positions, r

25、epresented against the rota-tion angle ??. At the measuring position 1# (Fig. 1(a)) wherethe axial distance to the kiln head is z = 0.5 m, the gas temper-ature and the wall temperature were approximately constant,with th

26、e value of 950 ?C and 350 ?C, respectively (Fig. 3). Fluc-tuating temperatures were shown by the three thermocouplesinserted into the material bed (r = 120 mm, 105 mm, 85 mm). Thefluctuation pattern of these lines corres

27、ponds with the transientmoving of thermocouples in the kiln cross-section. The thermocou-ples rotated in the direction of 180? → 90? → 0? → ?90? → ?180?.The temperature dropped steeply when the thermocouples sub-merged i

28、nto the material bed. During their passage through theFig. 5. Measured temperature profiles at the axial position z = 1.39 m.Fig. 6. Measured temperature profiles at the axial position z = 1.795 m.bed (for example 0? → ?

29、110? for the thermocouple r = 120 mm),the temperatures kept approximately constant. After that, thethermocouples came out of the bed into the hot gas and thetemperatures increased. Due to turbulent flow and buoyancy, the

30、radial gas temperature distribution is very inhomogeneous, as canbe seen from the thermocouples (r = 120 mm, 105 mm, 85 mm).Similar temperature profiles can be observed at the measuringpositions 2#–4# (Figs. 4–6). It can

31、 be seen that the tempera-tures within the material bed were not uniform (not as mosttheoretical models have assumed). Rather, there was a large tem-perature difference in the radial direction. The difference can bemore

32、than 100 ?C, as shown by the thermocouples r = 120 mm andr = 85 mm in Fig. 3. Therefore, the material bed cannot be treatedas isothermal, as has been done in the literature when model-ing the heat transfer in rotary kiln

33、s. However, with progressing ofthe material through the kiln, the difference became smaller andfinally the bed temperature approached the temperature of the kilnwall (Fig. 6).3.2. Temperature distribution within the bedW

34、ith the temperature profiles shown above, the mean bedtemperature at a certain radial depth can be determined. Fig. 7shows the temperature distributions within the material bedat the four axial positions along the kiln a

35、t steady state.The points with 45 mm ≤ r < 125 mm represent the temperatureswithin the material bed, whereas those points with r = 125 mmdenote temperatures of the inner wall of the kiln. Based onthe theoretical model

36、 for the rolling motion described in [5],the maximal thickness of the active layer of the bed wascalculated to be 16 mm. Thus, the range 45 mm ≤ r ≤61 mm cor-responds approximately to the region of the active layer. Thet

37、hermocouples stayed mostly in the passive layer, but wentshortly through the active layer when rotating together with thekiln.From Fig. 7, it can be seen that, near the kiln head at position 1#(z = 0.5 m) and position 2#

38、 (z = 0.8 m) the temperature differencewithin the bed was more than 100 ?C. Particles near the kiln wall(r = 120 mm) had the highest temperature. As the distance to thewall was increased, the temperature became lower. Th

39、is revealsthat regenerative heat was prevailing under the experimental con-figuration in this work. A preliminary calculation of the effectiveheat transfer coefficients ? demonstrated that ?Gas→Solid had a mag-nitude of

40、30 W/m2/K, while ?Wall→Solid was about 100 W/m2/K [6].As the material went further through the kiln, however, the temper-ature difference within the bed became smaller with a value of 37 ?Cand 12 ?C at position 3# (z = 1