서지주요정보
석탄의 미생물 탈황 및 고성능 기포탑 생물 반응기의 개발 = Microbial desulfurization of coal and development of a high performance bubble column bioreactor
서명 / 저자 석탄의 미생물 탈황 및 고성능 기포탑 생물 반응기의 개발 = Microbial desulfurization of coal and development of a high performance bubble column bioreactor / 류희욱.
저자명 류희욱 ; Ryu, Hee-Wook
발행사항 [대전 : 한국과학기술원, 1993].
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소장정보

등록번호

8003294

소장위치/청구기호

학술문화관(문화관) 보존서고

DCHE 93002

SMS전송

도서상태

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초록정보

Hydrodynamics and mass transfer characteristics in a bubble column with a new concept of radial gas sparger have been determined for carboxy methyl cellulose (CMC) solutions. Different concentrations of aqueous CMC solutions were used to simulate the pseudoplastic rheological behavior of mycelial broth. Experiments were carried out in a bubble column (0.115 m I. D. x 2.0 m high) made of transpartent Plexglas. A new flow regime map has been proposed. The churn-turbulent flow regime was observed over a wide range of gas velocity and liquid viscosity. As the gas velocity increase, the gas holdup ($\varepsilon_g$) increased in the bubbly flow regime, decreased in the churn-trubulent flow, and increased again in the slug flow regime. It decreased with liquid viscosity at a given gas velocity. The gas holdup obtained in the present bubble column was found to be 1.5~3 times higher than those in bubble columns or airlift reactors with a plate type gas sparger. The volumetric mass transfer coefficient, $k_L$ a significantly decreased with an increase in liquid viscosity. The $k_L$ a values in bubbly flow regime in the present study were much higher than those in bubble columns or airlift reactor with a plate type gas sparger in bubbly flow regime. The $\varepsilon_g$ and $k_L$ a data in both the bubbly and churn-turbulent flow regimes have been correlated with pertinent dimensionless groups. Oxygen transfer rate and gas holdup were measured in mycelial fermentation broths of Rhizopus oligosporus in a 28 L bubble column reactor with a radial gas sparger. These cultures exhibited a highly non-Newtonian flow behavior. The dependence of $k_L$ a on the rheological properties and aeration rate in mycelial fermentation broths in the present bubble columns was in a good agreement with a correlation based on the results of CMC solutions. On the other hand, $\varepsilon_g$ data were considerably higher than those for CMC solutions due to the existence of antifoam agent. The $k_L$ a values measured in fermentation broths were 30~40% lower than those in water. The values of $\varepsilon_g$ and $k_L$ a in our column are higher than those obtained in conventional bubble columns over a similar range of apparent viscosity. To remove pyritic sulfur from coal, a chemoautotrophic, acidophilic, iron-oxidizing bacterium, Thiobacillus ferrooxidans was employed. In all the experiments an anthracite coal obtained from Han Yang mining company was used. Effects of various process variables such as coal pulp density, salt concentration and particle size have been determined in shakd flask cultures. Above the concentration of 9K basal salts' medium, the influence of salt concentration on the rate and extent of sulfur oxidation was insignificant. Up to 80~98% of pyritic sulfur ($FeS_2$) could be removed within 11~15 days. The maximum rate of pyritic sulfur removal nearly increased with pulp density up to 50%(w/v) and reached a maximum level (1,417 mg S/L .d) at 70%(w/v). Higher rates and fractions of pyritic sulfur removal could be obtained at very higher pulp densities (up to 70 %(w/v)). Thus, the economic feasibility of the present microbial desulfurization process for the production of clean coal was quite higher. The optimum operating conditions were found to be the pulp density of 70%(w/v), the particle size smaller than 0.42mm, and the initial cell concentration of $10^9$ cells/mL. Microbial desulfurization of coal has been studied in an airlift slurry reactor of 12-L volume. Aeration was done at a rate of 1 vvm using an air-jet nozzle, which was sufficient to maintain homogeneous mixing of the coal slurry with up to 70% (w/v) of pulp density. The effects of coal pulp density and external $CO_2$ supply on the microbial pyrite removal have been determined. About 85~95% of pyritic sulfur in the coal could be removed by Thiobacillus ferrooxidans within 14~19 days. Higher sulfur removal rates and fractional removal have been obtained at higher coal pulp densities (up to 70% w/v). The obtained sulfur removal rates are found to be much higher (306~2,260 mg pyritic-S/L-day) than those (100~1,120 mg pyritic-S/L-day) reported in the literature for hard coals. Sulfur removal rates in the airlift bioreactor were about 10~59% higher than those in shake flask cultures because of sufficient supply of the nutrient gases ($O_2$, $CO_2$) and homogeneous mixing of coal slurry. Carbon dioxide supply was not the limiting factor for pyritic sulfur removal at lower coal pulp densities even when air is used for aeration. Whereas, the pyritic sulfur removal rate was improved by using a $CO_2$ enriched air at higher pulp densities. When the supply gas contained 5% of $CO_2$, the removal rates increased 17% and 43% at coal pulp densities of 40 and 70% (w/v), respectively. To evaluate the technical feasibility of microbial coal desulfurization during storage in coal dumps, microbial pyrite oxidation in a packed column reactor with Thiobacillus ferrooxidans has been investigated. In the percolation system of microbial desulfurization of coal, large particle sizes ($>$ 1.0 mm) and a narrow particle size distribution are required to ensure a favorable drainage of the liquid medium. When coal samples of 1~2 and 2~4 mm particle size were used, about 32~42% of pyrite sulfur was removed within 70 days. The measured rates of pyritic sulfur oxidation were in the rage of 348~803 mg S/kg coal-day. The sulfur removal rates in packed beds were about 15~25% of those suspension cultures. it was concluded based on the experiment results that a microbial percolation process was suitable for the desulfurization of high sulfur coals during a long term storage. The effect of surfactant on the rate of sulfur removal from coal by T. ferrooxidans has been determined to evaluate the feasibility of microbial desulfurization at a high coal pulp density. Most surfactants used for coal-water-mixture manufacturing catalyzed the oxidation of ferrous iron by T. ferrooxidans below 100 ppm, whereas the activity of T. ferrooxidans was depressed when the surfactant concentration was high. Anionic surfactants (Polymer sulfornate Na salt (CWM \#1001) and formaldehyde condensate of sodium naphthalene sulfornate (CWM \#1002 (n=4~5) and CWM\#1102 (n=10~20)) effectively reduced the activity of T. ferrooxidans and prevented the oxidation of ferrous iron to ferric iron, thereby minimizing the formation of acidic drainge from coal refuse and abandoned mines. Sodium polyacrylate (CWM\#1105), formaldehyde condensate of sodium naphthalene sulfornate (n=4, CWM\#1104), and Monopol NP \#1060(Nolyacrylate EO(50) adduct) below 5,000 ppm had no significant effect on the rate of pyrite leaching from coal and on the oxidation of ferrous iron. The agglomeration and sedimentation of coal particles at high coal slurry (65% (w/v)) could be prevented by the addition of these surfactants about 3,000 ppm. It was concluded that when these surfactants were added to coal slurry, the microbial desulfurization at a high pulp density were quite feasible. The microbial desulfurization from a bituminous coal has been investigated. The rate of pyritic sulfur removal increased with coal pulp density in a lower range. It showed a maximum at 20% (w/v) of pulp density (134mg S/L.d). The sulfur removal rates decreases significantly beyond 30% (w/v) of pulp densities due to the limitation of gaseous nutrients supply, the sedimentation of coal particles and inhibition by the leached organic material from coal. About 80~95% of pyritic sulfur was removed within 8 days when the pulp density was below 20% (w/v), whereas the fractional sulfur removal at higher pulp densities above 30%(w/v) was low. The kinetics of microbial removal of pyritic sulfur from coal was described by the Monod equation with respect to the accessible pyrite surface area. The rate of pyritic sulfur removal linearly increased with pyrite surface area. The addition of surfactants (CWM\#1105, CWM\#1104) increased the removal of pyritic sulfur at high coal pulp density. In an airlift reactor, about of 50% of pyritic sulfur in the bituminous coal was removed in 6 days at 50%(w/v) of coal pulp density.

서지기타정보

서지기타정보
청구기호 {DCHE 93002
형태사항 xxiii, 256 p. : 삽도 ; 26 cm
언어 한국어
일반주기 부록 : Ⅰ, Economic feasibilty for microbial desulfurization process of coal. - Ⅱ, Rew Data for microbial desulfurization of coal
저자명의 영문표기 : Hee-Wook Ryu
지도교수의 한글표기 : 김상동
공동교수의 한글표기 : 장용근
지도교수의 영문표기 : Sang-Dong Kim
공동교수의 영문표기 : Yong-Keun Chang
학위논문 학위논문(박사) - 한국과학기술원 : 화학공학과,
서지주기 참고문헌 : p. 219-230
주제 Non-newtonion fluids.
Bubbles.
Bioreactors.
Desulphurization.
비뉴톤류. --과학기술용어시소러스
기포탑. --과학기술용어시소러스
탈황. --과학기술용어시소러스
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