이미지 분석시스템을 이용한 부선컬럼에서 기포크기의 측정 = Measurement of Bubble Size in Flotation Column using Image Analysis System

다국어 초록 (Multilingual Abstract)

Bubble size in froth flotation has long been recognized as a key factor which affects the bubble residence time, the bubble surface area flux (Sb) and the carrying rate (Cr). This paper presents method of bubble size measurement, relationship between operating variables and gas dispersion properties in flotation column. Using high speed camera and image analysis system, bubble size has been directly measured as a function of operating parameters (e.g., superficial gas rate (Jg), superficial wash water rate (Jw), frother concentration) in flotation column. Relationship compared to measured and estimated bubble size was obtained within error ranges of ±15~20% and mean bubble size was 0.718mm. From this system the empirical relationship to control the bubble size and distribution has been developed under operating conditions such as Jg of 0.65~1.3cm/s, Jw of 0.13~0.52cm/s and frother concentration of 60~200ppm. Surface tension and bubble size decreased as frother concentration increased. It seemed that critical coalescence concentration (CCC) of bubbles was 200ppm so that surface tension was the lowest (49.24mN/m) at frother concentration of 200ppm. Bubble size tend to increase when superficial gas rate (Jg) decreases and superficial wash water rate Jw and frother concentration increase. Gas holdup is proportional to superficial gas rate as well as frother concentration and superficial wash water rate (at the fixed superficial gas rate).

국문 초록 (Abstract)

기포크기는 컬럼부선에서 기포체류시간, 기포표면적플럭스(Sb) 및 운송율(Cr)에 영향을 미치는 중요 변수로 인식되고 있다. 본 논문은 부선컬럼에서 기포크기의 측정방법, 가동변수들의 관계 그리고 가스분산특성을 논한다. 기포크기는 고속카메라와 이미지 분석 시스템을 이용하여 가동변수들(가스속도, 세척수속도, 기포제농도)의 조건에 따라 부선컬럼에서 직접적으로 측정되었다. 각 측정과 산정된 기포크기 값들을 비교한 관계식이 ±15~20의 오차범위 내에서 도출되었고 평균 기포크기(Sauter mean diameter)는 0.718mm로 확인되었다. 본 시스템으로부터 기포크기 및 분포를 조절할 수 있는 경험식이 가동조건들(Jg: 0.65~1.3cm/s, JW: 0.13~0.52cm/s, frother concentration: 60~200ppm) 하에서 개발되었다. 기포제농도의 증가는 표면장면과 기포크기를 감소시킨다. 임계병합농도는 표면장력이가장 낮은 49.24mN/m일 때인 기포제농도 200ppm이라고 판단된다. 공기속도의 감소, 기포제농도 및 세척수속도의 증가에 따라 기포크기가 감소하는 경향을 보였다. 가스홀드업은 가스속도와 비례관계에 있으며 고정된 가스속도 조건에서 기포제농도 및 세척수속도와 비례관계였다.

참고문헌 (Reference)

1 Nesset, J. E., "Some gas dispersion characteristics of mechanical flotation machines" 19 (19): 807-815, 2006

2 Rodrigues, R. T., "New basis for measuring the size distribution of bubbles" 16 (16): 757-765, 2003

3 한오형, "Microbubble Column에 의한 鱗狀黑鉛의 浮選에 관한 硏究" 한국자원리싸이클링학회 15 (15): 37-44, 2006

4 Vadlakonda, B., "Hydrodynamic study of two phase flow of column flotation using electrical resistance tomography and pressure probe techniques" 184 : 168-187, 2017

5 Masliyah, J. H., "Hindered settling in a multi-species particle system" 34 (34): 1166-1168, 1979

6 Vinnett, L., "Gas dispersion measurements in mechanical flotation cells : Industrial experience in Chilean concentrators" 57 : 12-15, 2014

7 Schwarz, S., "Gas dispersion measurements in industrial flotation cells" 19 (19): 554-560, 2006

8 Gomez, C. O., "Gas dispersion measurements in flotation cells" 84 (84): 51-58, 2007

9 Ravichandran, V., "Gas dispersion characteristics of flotation reagents" 235 : 329-335, 2013

10 Banisi, S., "Effect of solid particles on gas holdup in flotation columns-I" 50 (50): 2329-2334, 1995

11 Vazirizadeh, A., "Effect of particles on bubble size distribution and gas hold-up in column flotation" 157 : 163-173, 2016

12 Cho, Y. S., "Effect of flotation frothers on bubble size and foam stability" 64 (64): 69-80, 2002

13 Finch, J. A., "Column Flotation" Pergamon Press 16-18, 1991

14 Tan, Y. H., "Bubble size, gas holdup and bubble velocity profile of some alcohols and commercial frothers" 119 : 1-5, 2013

15 Chen, F., "Bubble size measurement in flotation machines" 14 (14): 427-432, 2001

16 Yianatos, J. B., "Bubble size estimation in a bubble swarm" 126 (126): 37-44, 1988

17 Lin, B., "Bubble size estimation for flotation processes" 21 (21): 539-548, 2008

18 Lichti, M., "Bubble size distributions with a shadowgraphic optical probe" 60 : 164-170, 2018

19 Cho, Y. S., "Bubble coalescence and its effect on dynamic foam stability" 80 (80): 299-305, 2002

20 Ata, S., "A study of bubble coalescence in flotation froths" 72 (72): 255-266, 2003