As industry continues to develop, the amount of various recalcitrant substances that cannot be removed by conventional wastewater treatment has increased in modern society. The SCFs (Soluble Cutting Fluids) used in metalworking processes contain many chemical substances, such as mineral oils, anticorrosive agents, extreme-pressure additives and stabilizers, as well as high concentrations of organics. Recently, electrolysis has been expected to become an alternative to conventional processes and to be useful in various wastewater treatments. Electrolysis is a highly adaptable industrial wastewater treatment method, having a high efficiency, short processing time, and simple equipment composition, regardless of the biodegradable nature of the contaminants. The effects of operating time, current density, and electrolyte on COD removal of waste SCFs have been studied using the stainless steel (SUS316) electrode in a batch type reactor. The results were as follows. ① Without electrolytes, when the current density was adjusted to 40 A/m2, 60 A/m2, and 80 A/m2, the removal efficiencies of the COD were 25.0%, 37.7%, and 49.1% after 60 min, respectively. ② In the comparison between NaCl (5 ~ 10 mM) addition and non-addition, the removal efficiency with NaCl was higher than for without after 60 min for all current densities. ③ In the comparison between Na2SO4 (5 ~ 10 mM) addition and nonaddition, the removal efficiency with Na2SO4 showed no significant difference to that with NaCl at all current densities.

Soluble cutting fluids (SCFs) have been used in metal machining processes to improve the quality of metal processing equipment and products in modern society. Because the characteristics among metal machining processes differ, various types of cutting fluids are manufactured to enhance the cutting efficiency of different metals. Although SCFs are useful and essential materials, particular treatment is required attributable to the high concentration of nitrogen materials and chemical oxygen demand (COD). In this study, the removal efficiency of total nitrogen (T-N) contained in SCFs was analyzed using electrochemical treatment. The electrode was made of 316 stainless steel, which had been perforated to prevent an imbalanced sample concentration in the reactor. Cathodic and anodic electrodes were alternately inserted into an acrylic reactor. The removal efficiency of T-N in SCFs using 40 A/m2, 60 A/m2, and 80 A/m2 current density, was 48.2%, 61.5% and 69.3%, respectively. The removal efficiency of T-N in SCFs with the addition of 0, 5 mM, and 10 mM NaCl was 69.3%, 74.6%, 77.6%, respectively.

화석에너지 자원 고갈 및 경제발전에 따른 산업화가 가속화되면서 폐기물의 발생량이 지속적으로 증가하여 폐기물 에너지화 기술에 대한 관심이 급증하고 있다. 공정상에 발생하는 폐기물 중에서 특히, 메탄올의 경우에는 분리가 쉬우며 저장성이 용이하고 연료전지 사용 및 수소에너지로의 변환이 용이하므로 많은 전원장치에서 응용이 가능하다. 공정상에서 비상전원의 경우에는 배터리 또는 연료전지를 이용하게 된다. 이때 PEM 연료전지를 이용할 경우 배터리에 비해 에너지 밀도가 현저히 높기 때문에 장시간 비상전원 공급이 가능하다. 메탄올의 경우에는 다른 폐기물에 비해서 높은 수소 : 탄소 비를 가지며 낮은 끓는점을 가지면서 공정 폐기물에서 쉽게 추출할 수 있으며 저장하는데 별도의 장치가 필요 없고 또한 낮은 온도에서 간단한 조건에서 쉽게 개질이 가능하므로 연료전지 시스템에 적용이 용이하다. 본 연구에서는 공정상 추출한 메탄올을 비상전원장치의 연료로 사용한 PEM 연료전지에 적용이 가능한 메탄올 개질 반응에 대한 연구를 수행하였다. 수소를 생산하는 개질반응에는 열분해 반응, 수증기 개질 반응, 부분 산화 반응 및 수증기 개질 반응 및 부분 산화 반응의 조합으로 이루어진 자열 개질 반응이 존재한다. 4가지의 개질반응에 대한 각각의 실험을 수행하여 비상전원시스템으로의 적합성에 대한 연구를 수행하였다. 비상전원시스템의 경우에는 구조가 간단하고 부가 장치가 적을수록 가공, 제작 및 장치 구동 면에서 유리하고 또한 성공적인 비상 PEM 연료전지 구동을 위한 수소 생산을 위해서는 연료 개질 시스템은 복잡하게 구성되며 연료전지의 구동 온도가 낮을수록 더 많은 과정을 거치게 된다. 비상전원시스템에서 동적 부하 변동에 빠른 응답성을 가지며 동시에 메탄올에 대해서 비교적 안정적인 운전이 가능하며 외부 열원의 사용을 최소화 할 수 있는 개질 반응 연구를 수행하였다. 다양한 개질 반응에 대한 수소 발생률 및 BOP(Balance of Plant)의 비교 검증을 통하여 비상전원시스템에 가장 적합한 개질 반응에 대한 선택을 하였으며 선택된 개질 반응을 이용하여 비상 PEM 연료전지 전원장치 시스템에 적용시켰다. 이는 비상 PEM 연료전지 전원장치 뿐만 아니라 다양한 연료 처리 장치에 적용 가능할 것으로 판단된다.

In this study, pressure drop was measured in the pulse jet bag filter without venturi on which 16 numbers of filter bags (Ø140 × 850 ℓ) are installed according to operation condition(filtration velocity, inlet dust concentration, pulse pressure, and pulse interval) using coke dust from steel mill. The obtained 180 pressure drop test data were used to predict pressure drop with multiple regression model so that pressure drop data can be used for effective operation condition and as basic data for economical design. The prediction results showed that when filtration velocity was increased by 1%, pressure drop was increased by 2.2% which indicated that filtration velocity among operation condition was attributed on the pressure drop the most. Pressure was dropped by 1.53% when pulse pressure was increased by 1% which also confirmed that pulse pressure was the major factor affecting on the pressure drop next to filtration velocity. Meanwhile, pressure drops were found increased by 0.3% and 0.37%, respectively when inlet dust concentration and pulse interval were increased by 1% implying that the effects of inlet dust concentration and pulse interval were less as compared with those changes of filtration velocity and pulse pressure. Therefore, the larger effect on the pressure drop the pulse jet bag filter was found in the order of filtration velocity(Vf), pulse pressure(Pp), inlet dust concentration(Ci), pulse interval(Pi). Also, the prediction result of filtration velocity, inlet dust concentration, pulse pressure, and pulse interval which showed the largest effect on the pressure drop indicated that stable operation can be executed with filtration velocity less than 1.5 m/min and inlet dust concentration less than 4 g/m3. However, it was regarded that pulse pressure and pulse interval need to be adjusted when inlet dust concentration is higher than 4 g/m3. When filtration velocity and pulse pressure were examined, operation was possible regardless of changes in pulse pressure if filtration velocity was at 1.5 m/min. If filtration velocity was increased to 2 m/min. operation would be possible only when pulse pressure was set at higher than 5.8 kgf/cm2. Also, the prediction result of pressure drop with filtration velocity and pulse interval showed that operation with pulse interval less than 50 sec. should be carried out under filtration velocity at 1.5 m/min. While, pulse interval should be set at lower than 11 sec. if filtration velocity was set at 2 m/min. Under the conditions of filtration velocity lower than 1 m/min and high pulse pressure higher than 7 kgf/cm2, though pressure drop would be less, in this case, economic feasibility would be low due to increased in installation and operation cost since scale of dust collection equipment becomes larger and life of filtration bag becomes shortened due to high pulse pressure.

Method 9 is a reference method established by U.S. Environmental Protection Agency (EPA) to quantify plume opacity by the certified observer. Later, digital Optical Method (DOM) was developed to quantify plume opacity from digital photographs for bright and dim conditions. However, there is a limitation for the use of Method 9 and DOM to quantify the plume opacity especially for dim condition. In this paper, DIM-DOM system was used instead of DOM to quantify plume opacity during dim condition. Opacity readings provided by DIM-DOM were compared with the opacity values obtained with the reference in-stack transmissometer of the smoke generator. The individual opacity error results demonstrated that DIM-DOM met Method 9’s requirements. The individual opacity values ranging from 0 to 100% compare well to the corresponding opacity results from the in-stack transmissometer results meeting USEPA’s Method 9 IOE requirement of ≤15%. These results are encouraging and indicate that DIM-DOM has the potential to quantify plume opacity during dim condition.