• Korean Chemical Engineering Research
• /
• v.50 no.5
• /
• pp.837-842
• /
• 2012

A pilot scale circulating fluidized boiler (CFB) for refuse derived fuel (RDF) is designed and constructed to demonstrate a performance of CFB technology for waste fuel utilization. The boiler has a design capacity of 6 MWth with $400^{\circ}C$ 38 ata steam generation performance. The maximum steam rate of the boiler was about 8 ton/h. The main component of the fuel was RDF (Refuse Derived Fuel) with high volatile contents and showed fast ignition and easy combustion. The pilot plant showed over 99.5% of combustion efficiency. Stable operation of RDF CFBC depended on the content of non combustion materials other than ash and fast removal of them. Emission level was under legal limit except that of HCl without external flue gas treatment facilities. Also about 60% of fuel chlorine was absorbed to fly ash particles. For HCl emission control flue gas treatment technology is required such as wet and dry scrubber in order to comply with Korean regulation.

• 한국신재생에너지학회:학술대회논문집
• /
• 2010.06a
• /
• pp.110.2-110.2
• /
• 2010

현재 상용가능한 연소전 $CO_2$ 포집 기술은 습식 스크러빙 방식으로 고온의 합성가스를 상온 수준으로 온도를 낮춘 후 $CO_2$를 포집해야 하고 포집된 $CO_2$의 압력이 낮아 재압축하여 저장소로 보내야 함에 따라 큰 폭의 열효율 손실이 불가피하다. 고온 고압에서 이산화탄소를 포집할수 있는 고체 흡수제를 이용할 경우 이산화탄소 포집 치 저장 추가에 따른 시스템 효율 저하를 최소화할 수 있다. 고체 $CO_2$ 흡수제는 서로 연결된 두 개의 유동층 반응기를 순환하면서 흡수탑에서는 합성가스 중의 $CO_2$를 흡수하고 재생탑에서는 고온의 수증기와 접촉하여 흡수된 $CO_2$를 다시 배출함으로써 재생된다. 따라서 건식 재생 $CO_2$ 흡수제는 유동층 공정에 응용가능한 물성과 함께 높은 $CO_2$ 흡수능과 빠른 반응성이 요구된다. 본 연구에서는 유동층 공정에 적합한 물성을 가진 연소전 $CO_2$ 포집용 고체 흡수제를 분무건조법으로 제조하였으며, 모사 합성가스를 이용하여 열중량분석기와 기포유동층반응기를 이용하여 $200^{\circ}C$ 흡수, $400^{\circ}C$ 재생, 압력 20 bar 조건으로 반응성을 측정하였다. 개발된 고체 $CO_2$ 흡수제는 열중량분석기에서는 반응 후 10-13 wt%의 무게증가를 나타내었고 기포유동층반응기에서는 8-10 wt%의 $CO_2$ 흡수능을 보여주었다. 특히 수증기의 함량이 10% 이상에서 높은 흡수능을 나타내어 수증기가 반응에 크게 작용하고 있음을 알 수 있었다.

• Applied Chemistry for Engineering
• /
• v.19 no.1
• /
• pp.66-72
• /
• 2008

Manganese hydrogen phosphate hydrate, $MnHPO_4{\cdot}2.25H_2O$, is a major constituent of the pre-conditioning compositions for the manganese phosphate coating treatment over carbon steel substrate. This compound is conventionally produced by the synthesis in the aqueous solution process followed by the filtration and drying processes and a series of size reduction and classification processes in dry state. However, it is evident that the conventional process is neither environment-friendly nor cost-effective. In this work, a new process principle was examined based on the controlled double-jet precipitation technology to produce the manganese chemical product of fairly uniform particle size distribution in an aqueous solution media. The effects of stabilizing agents were comparatively studied by the scanning electron microscope analysis in a uniformity point of view of the resulting particle size. Polyvinylpyrrolidone and Gum Arabic were excellent in controlling the crystal growth step, resulting in fairly uniform size distributions of the particles from the controlled double-jet process.

• Journal of Korean Society of Steel Construction
• /
• v.10 no.4 s.37
• /
• pp.657-666
• /
• 1998

This study presents an effective dual algorithm for the optimal design of steel structures with displacement constraints. The dual method can replace a primary optimization problem with a sequence of approximate explicit subproblems with a simple algebraic structure. Since being convex and separable, each subproblem can be solved efficiently by the dual method. Specifically, this study uses the principle of virtual work to obtain the displacement constraint equations with an explicit form and adds the linear regression equation expressing the relationships between the cross-section properties to the dual algorithm to reduce the number of design variables. Furthermore, this study deals with the discrete optimization problem to select members with the standard steel sections. Through numerical analyses, the proposed method will be compared with the conventional optimality criteria method.

• Proceedings of the Materials Research Society of Korea Conference
• /
• 2003.03a
• /
• pp.222-222
• /
• 2003

나노크기 금속입자가 분산된 세라믹 나노복합재료는 향상된 기계적 특성과 함께 독특한 전기적, 자기적 특성을 보여주어 새로운 기능성 재료로의 응용가능성을 갖고 있다. 그러나 소결 중의 반응이나 입자성장 등으로 형성된 반응상 또는 조대한 입자상이 세라믹 기지의 입계 등에 존재한다면, 나노크기 금속상 분산에 의한 기계적 특성의 향상과 독특한 기능성 부여라는 장점들이 없어지게 된다. 따라서 요구되는 특성을 구현할 수 있는 금속분산 나노복합재료의 제조를 위해서는 미세조직 제어를 위한 최적의 제조공정 확립과 미세조직과 특성 등의 관계에 대한 연구가 요구된다. 본 연구에서는 기지상으로 A1$_2$O$_3$를, 분산상으로는 저융점 금속이며 일반적인 A1$_2$O$_3$의 가압소결시에 (약 140$0^{\circ}C$) 액상으로 존재하는 금속 Cu를 선택하여 조성이 5 vol% Cu가 되도록 복합재료를 제조하였다. $Al_2$O$_3$와 CuO 원료분말들은 습식 및 건식 볼 밀링을 통하여 균일한 분말혼합체로 제조되었다. 혼합분말은 열간가압소결기 내에 장입한 후 35$0^{\circ}C$에서 30분 동안 H$_2$가스를 흘려주며 CuO를 Cu로 환원 처리하였다. 계속해서 H$_2$분위기를 유지하며 승온한 후, 각각 1000-145$0^{\circ}C$에서 분위기를 Ar 으로 치환하였다. 소결은 145$0^{\circ}C$에서 30 ㎫의 압력으로 1시간동안 행하였다 소결한 시편들은 직사각형 형태로 가공하였으며 표면은 0.5$\mu\textrm{m}$의 다이아몬드 입자로 연마하였다. XRD, SEM 및 TEM을 이용하여 상분석 및 미세조직관찰을 행하였다. 파괴강도는 3중점 굽힘 법으로 (3-point bending test) 측정하였다. 이때 시편 하부의 지지 점간의 거리는 30mm, cross-head 속도는 0.5 mm/min으로 하였고 5개의 시편을 측정하여 평균값을 구하였다.

• Journal of Korean Society for Atmospheric Environment
• /
• v.14 no.4
• /
• pp.273-280
• /
• 1998

The investigation on the removal of 502 gas fro.In flue gas which causes serious air pollution was made by using a semi dry flue gas desulfurization method. Experiments were carried out as a function of process variables which would affect SO2 removal efficiency. Process variables inclilded SO2 inlet concentration, inlet temperature of simulated flue gas, sorbent weight fraction, and volume flow rate of sorbent slurry. In this study, used sorbent was Ca(OH), and simulated flue gas was prepared by mixing pure SO2 gas with air. Experimental conditions were varied at 140~18$0^{\circ}C$ of inlet temperature of the simulated flue gas, 500~2000ppm of inlet SO2 concentration, 0.4~1.0% of sorbent concentration, and 10~25 mL/min of flow rate of sorbent slurry. Among process variables, inlet concentration of SO2 was found to be the most significant factor to affect SO2 removal efficiency. The concentration of Ca(OH2) had a lower effect on SO2 removal than SO2 inlet concentration removal amount was 0.108, 0.141, 0.153 g SO2/g Ca(OH)2 respectively- As 200 mmol of HNO3 was added into slurry to improve removal efficiency, initial pH was maintained and solubility of slurry increased, so that removal efficiency elevated. Adding over 200 mmol of HNO3 into slurry caused removal efficiency lower. Therefore it could be concluded the optimum was 200 mmol of HNO3 input.

• Journal of Powder Materials
• /
• v.26 no.6
• /
• pp.471-476
• /
• 2019

Additively manufactured metallic components contain high surface roughness values, which lead to unsatisfactory high cycle fatigue resistance. In this study, high cycle fatigue properties of selective laser melted Ti-6Al-4V alloy are investigated and the effect of dry-electropolishing, which does not cause weight loss, on the fatigue resistance is also examined. To reduce the internal defect in the as-built Ti-6Al-4V, first, hot isostatic pressing (HIP) is conducted. Then, to improve the mechanical properties, solution treatment and aging are also implemented. Selective laser melting (SLM)-built Ti64 shows a primary α and secondary α+β lamellar structure. The sizes of secondary α and β are approximately 2 ㎛ and 100 nm, respectively. On the other hand, surface roughness Ra values of before and after dry-electropolishing are 6.21 ㎛ and 3.15 ㎛, respectively. This means that dry-electropolishing is effective in decreasing the surface roughness of selective laser melted Ti-6Al-4V alloy. The comparison of high cycle fatigue properties between before and after dry-electropolished samples shows that reduced surface roughness improves the fatigue limit from 150 MPa to 170 MPa. Correlations between surface roughness and high cycle fatigue properties are also discussed based on these findings.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
• /
• v.6 no.3
• /
• pp.233-244
• /
• 2008

A conceptual design study for a pyroprocesing facility, has been carried out in this study, which is available for the recovery of uranium and transuranic elemental group(TRU), that is, reusable as a nuclear fuel especially in a next generation-type reactor. The scale of this facility has been chosen as 20 kg HM/batch, comparatively small engineering size in order to collect scale-up data for the design of a commercial facility as well as to get operational experience. The spent fuel to be handled in this process is as follows : 3.5 % enriched uranium fuel, 35,000MWd/tU and 5-year cooled. The major items considered in the conceptual study are a building lay-out including various hot cells, safety management of the process operation in conjunction with material balance control, radiation safety, inert atmosphere control in shielded hot cells, and criticality control of uranium and TRU products.

• Journal of the Korean Magnetics Society
• /
• v.4 no.3
• /
• pp.233-238
• /
• 1994

The effect of die upset and heat treatment on the magnetic properties of mechanically ground $Nd_{16}Fe_{78}B_{6}$ alloys has been studied. Although stripe domain patterns parallel to the compression direction were observed after die upset, it was found that crystallographic c-axes of a specimen were not completely aligned along the compression direction' which resulted in the decrease of Br. The average grain size of a die-upset specimen annealed for 5 hours at $1000^{\circ}C$ was about $20\mu\textrm{m}$, resulting in reduced values of Br and $_{i}H_{c}$. The maximum magnetic properties (Br=7.8 kG and $(_{i}H_{c}=14\;kOe) were obtained from the magnet die-upset at $750^{\circ}C$ using the alloy powder ground for 13 hours.

• Geotechnical Engineering
• /
• v.3 no.2
• /
• pp.55-70
• /
• 1987

An analytical solution procedure is described to estimate the developed passive lateral earth Pressures behind a vertical rigid retaintng wall rotating about its toe into a mass of cohesionless soil. Various stases of wall rotation, starting from an at-rest state to an initial Passive state to a full Passive state, are considered in the analysis. Condition of failure defined by a modified Mohr-coulomb criterion, together with equilibrium conditions, is used to obtain the necessary equations for the solution. Using methods of stress characteristics and numerical finite difference, a complete solution within and on the boundaries of the entire solution domain is made possible. The variations of the soil shear strength and the wall friction at various depths and stages of wall rotation are also taken into account in the analysis. The results predicted by the developed method of analysis are compared with those obtained from the experimental model tests on loose and dense sand. The comparisons show good agreements at various stages of retaining wall rotation Fin- ally, results of analytical parametric study are presented to demonstrate the effects of wall fric- tion on the resultant thrust and distribution of developed lateral earth pressures.