정삼투 여과막(FO) 기술 분야는 해수 담수화에서 이미 다양한 연구가 진행되었으나, 하폐수 처리 분야의 적용에서는 상대적으로 많은 연구가 필요한 상황이다. FO 기술은 비 다공성 특성막과 각 용액 사이의 삼투압 차이를 이용하여 원폐수로부터 수분을 비롯하여, 질소-인과 같은 이온성 물질까지 분리할 수 있다. 본 연구에서는 FO 막을 혐기성 유동상 미생물반응기(AFBR)를 통해 처리된 처리수 내 존재하는 질소(주로 암모니아성 질소)를 제거하기 위해 적용되었다. 유도용액(Draw Solution, DS)의 종류(NaCl, CaCl2, Na2CO3)에 따라 투과량은 NaCl, CaCl2, Na2CO3 순으로 높게 나타났으며, 암모니아성 질소의 배제율은 각각 42.25%, 78.83%, 70.35%으로 나타났다.

실 산성 도금폐수를 입상활성탄(GAC)이 유동메디아로 첨가된 유동상 멤브레인 반응기를 이용하여 처리하였다. GAC 유동조건에서 적용 투과플럭스에 대해 시간에 따른 흡입압의 증가는 관찰되지 않았다. 폐수의 중성 pH에서 파울링 속도는 산성 조건에 비해 GAC 유동조건에서 크게 감소하였다. 해당 폐수의 용액 pH 증가는 입자크기의 증가를 가져왔고 이는 멤브레인 표면에서 상대적으로 성긴 구조의 케이크층 형성을 야기시켰다. 유동상 멤브레인 반응기에서 GAC 유동 하에 95% 이상의 COD 제거율이 관찰되었으며 총부유물질은 거의 완벽하게 제거되었다. 실 도금폐수의 pH에서, 유동상 멤브레인 반응기의 구리 및 크롬의 제거는 거의 관찰 되지 않았다. 그러나 pH를 중성으로 증가 시켰을 시 구리와 크롬의 제거율은 각각 99%와 94%까지 증가를 하였다. 적용해 준 pH에 상관 없이, 시안의 경우 95% 이상의 제거율을 달성하였다. 이는 유기물과 시안 착물 형성으로 인해 유동상 멤브레인 반응기 내 GAC의 강한 흡착으로 제거된 것으로 사료된다.

하수처리 혐기성 유동상 생물반응기(Anaerobic Fluidized Bed Bioreactor : AFBR)는 높은 표면적을 갖는 입상활 성탄을 유동 메디아로 적용함으로써 생물막 형성 및 유지에 유리하며 이로 인해 우수한 유기물 제거 효율을 나타내나 처리된 유출수 내의 질소와 같은 영양염류의 잔존이 여전히 문제로 남아있다. 본 연구에서는 AFBR에 의해 처리된 유출수 내의 질소 배제를 위하여 정삼투막(FO membrane)을 유도용액의 종류와 농도에 따라 적용하였다. 실험결과 유출수의 총질소 배제 효율 은 FO막에 적용하는 유도용액(draw solution : DS)의 종류 및 농도에 크게 의존하였다. 유도용액 농도가 증가함에 따라 FO막의 수투과량이 증가하였으며, 1 M의 NaCl을 유도용액으로 사용한 경우 총질소 배제 효율은 55%이었으나 1 M의 glucose를 유도용액을 사용한 경우 거의 완벽한 총질소 배제 효율을 나타내었다. AFBR 유출수를 FO막으로 24시간 동안 여과를 진행하 였으나 파울링에 의한 수투과량의 감소는 관찰되지 않았다.

The Anaerobic fluidized bed bioreactor (AFBR) treating synthetic wastewater to simulate domestic sewage was operated under GAC fluidization to provide high surface area for biofilm formation. Although the AFBR achieves excellent COD removal efficiency due to biological activities, concerns are still made with nutrient such as nitrogen remaining in treated wastewater. In this study, FO membrane was applied to treat the effluent produced by AFBR. Removal efficiency with total nitrogen (TN) was investigated with draw solution (DS, NaCl) and hydrodynamic condition (i.e., recirculation flow rate) along FO membranes. Permeability of FO membrane increased with increasing DS concentration. About 85% of TN removal efficiency was observed with the FO membrane using 1 M of NaCl DS. During operational period of a day, no permeate flux decline was observed.

The non-reacting flow field and the movement of sand particles inside a 30MW circulating fluidized bed combustor is numerically simulated via the finite volume method. The primary air is supplied through 23x23 array of nozzles located on the bottom and the secondary air is supplied through 12 inlet pipes located on the side walls. The steady state velocity field shows that a very complex flow pattern is formed in the lower part of the combustor. As the gas moves upward, the velocity magnitude decreases and the gas exits the combustor after hitting the top wall. To investigate the behavior of sand particles with different diameters, a particle tracking calculation is performed by introducing sand particles continuously at the z=3 m plane. For the given air flow rate condition, sand particles smaller than 0.3 mm show a complex movement pattern near the secondary air inlet and then rise toward the outlet.

To improve dispersibility of cereal powder without additives, granulation of cereal powder was conducted using fluidized- bed granulator. Operation condition was sample 300 g, internal temperature 40°C, ventilation speed 30-90 m3/ h, inlet temperature 90°C and spray pressure 2.5 bar. The amount of distilled water (20-45%) as binder, granulation time (10-15 min) and drying time (3-10 min) were controlled. Mean diameter over volume (Brouckere mean, D4,3) was increased from 123 μm to 263 μm and dispersibility was improved from 73% to 92.25% at experiment conditions. Wettability (wetting time) was drastically decreased from 5,000 second to 7 second. Granulation of cereal powder did not affect sinkability and mean diameter over volume as wet analysis was about the same between raw and granulated cereals. Such phenomenon means that granulation with only water as binder enables cereal powder to disperse in water or milk without rapid sedimentation.

평관형 알루미나 세라믹 멤브레인을 적용한 실험실 규모의 단독 혐기성 유동상 멤브레인 생물반응기 (Anaerobic Fluidized Bed Ceramic Membrane Bioreactor, AFCMBR) 하수처리 적용 가능성을 평가하였다. 단독 AFCMBR은 25℃에서 395일 간 합성폐수의 평균 유입 COD 260 mg/L에서 연속운전 되었다. 운전기간 동안 약 25 mg/L의 NaOCl 용액을 주입하여 주기적인 유지세정으로 멤브레인 투과플럭스 14.5-17 L/m².hr 달성이 되었다. 투과수의 용해성 COD는 1시간 HRT 에서 23 mg/L 이었고 고형물 발생량은 0.014 gVSS/gCODremoved였다. 단독 AFCMBR 운전 요구 전기에너지는 0.038 kWh/m³ 이었고 생산되는 메탄발생 전기에너지의 약 17%에 해당되었다.

유동층가스화기는 경제적으로 기술적으로 입증된 기술로서 가장 상용화에 가까운 가능성을 보여주고 있다. 그러나 한국에서는 설계, 현장문제 해결뿐 아니라 파일럿 규모의 설비 운전 등이 부족하 여 상용화에 이르지 못하고 있다. 본 연구에서는 바이오매스의 가스화를 위하여 3 MWth 급 순환유동 층(CFB) 반응기를 개발하여 운전하였다. 유동층반응기는 순환유동층 반응기와 기포유동층 반응기로 구 성되었으며 타르와 산성가스를 제거하기 위하여 세라믹필터, 급속냉각, 습식스크러버를 사용하였다. 3 MWth 급 바이오매스 가스화기의 최적 운전조건을 도출하기 위하여 equivalence ratio에 따른 영향을 조사하였다

A black nickel oxide powder, one of the commercial nickel oxide ores, was reduced by hydrogen gas in a batchtype fluidized-bed reactor in a temperature range of 350 to 500 oC and in a residence time range of 5 to 120 min. The hydrogen reduction behavior of the black nickel oxide was found to be somewhat different from that of green nickel oxide ore. For the black nickel oxide, the maximum temperature (below which nickel oxide particles can be reduced without any agglomeration) was significantly lower than that observed for the green nickel oxide. In addition, the best curve fittings of the Avrami model were obtained at higher values of the overall rate constant “k” and at lower values of the exponent “m”, compared to those values for the green nickel oxide. It may be inferred from these results that the hydrogen reduction rate of the black nickel oxide is faster than that of the green nickel oxide in the early stages, but the situation reverses in the later stages. For the black nickel oxide ore, in spite of the low temperature sintering, it was possible to achieve a high degree fluidized-bed reduction at lower temperatures and at lower gas consumption rates than was possible for the green nickel oxide. In this regard, the use of black nickel oxide is expected to yield a benefit if its ore price is sufficiently lower than that of the green nickel oxide.

A commercial NiO (green nickel oxide, 86 wt% Ni) powder was reduced using a batch-type fluidized-bed reactor in a temperature range of 500 to 600 oC and in a residence time range of 5 to 90 min. The reduction rate increased with increases in temperature; however, agglomeration and sintering (sticking) of Ni particles noticeably took place at high temperatures above 600 oC. An increasing tendency toward sticking was also observed at long residence times. In order to reduce the oxygen content in the powder to a level below 1 % without any sticking problems, which can lead to defluidization, proper temperature and residence time for a stable fluidized-bed operation should be established. In this study, these values were found to be 550 oC and 60 min, respectively. Another important condition is the specific gas consumption rate, i.e. the volume amount (Nm3) of hydrogen gas used to reduce 1 ton of Green NiO ore. The optimum gas consumption rate was found to be 5,000 Nm3/ton-NiO for the complete reduction. The Avrami model was applied to this study; experimental data are most closely fitted with an exponent (m) of 0.6 ± 0.01 and with an overall rate constant (k) in the range of 0.35~0.45, depending on the temperature.

The present study prepared molybdenum trioxide (MoO3), the most important intermediate of molybdenum metal, by using a fluidized bed reactor for the thermal decomposition of ammonium molybdate (AM) in the presence of an air flow. During the process of fluidizing the sample inside the reactor, the reaction time and temperature were optimized with a close analysis of the X-ray diffraction (XRD) data and with thermogravimetric analysis (TGA). In particular, the temperature level, at which the AM decomposition is completed, is very important as a primary operating parameter. The analysis of the XRD and TGA data showed that the AM decomposition is almost completed at ~350 oC with a reaction time of 30 min. A shorter reaction time of 10 min. required a higher reaction temperature of ~500 oC with the same air flow rate to complete the AM decomposition. A sharp rise in the decomposition efficiency at a temperature ranging between 320 and 350 oC indicated a threshold for the AM decomposition. The operating conditions determined in this study can be used for future scale-ups of the process.