화학공정에 대한 전과정 평가 기법의 개발과 적용

학위논문(박사) - 한국과학기술원 : 화학공학과, 1999.2, [ xiv, 179 p. ]The purpose of this thesis has been to increase the transparency of LCA(Life Cycle Assessmemt) as a decision-supporting tool and to improve the scientific basis of LCA, with the greatest focus on the chemical processes. Improving the scientific basis of LCA thus does not mean that new scientific theories are proposed or empirical experiments performed but that a method is designed based - as far as possible on the present status of relevant scientific disciplines. First, a LCA framework is proposed which distinguishes four different components: goal and scope definition, inventory, impact assessment and interpretation and the framework which is now in development in ISO. As far as possible, the ISO LCA framework and terminology is followed in this thesis. Goal & scope definition is concerned with defining the goal of the study in relation to the intended application. Application of LCA always involves some kind of comparison, for which a unit of use should be specified which is to form the basis for comparison. The unit is based on the function of the products to be compared, and is called the functional unit. In order to make a quantified survey of the environmental inputs and outputs of a product system, the boundary between the designated product system and other product systems must be determined, and some cut-off point set for the infinite regression of processes needed to produce inputs for other processes. Classification and characterization in impact assessment and interpretation are also discussed. In the classification component, the resource extractions and emissions associated with the life cycle of a product are translated into contributions to a number of environmental problem types, such as resource depletion, global warming, ozone depletion, acidification, and so on. To the end, each extraction and emissions is multiplied by a classification factor (or equivalency factor according to SETAC terminology) and the multiplication results are aggreg...한국과학기술원 : 화학공학과

도금 공장 폐수로부터 Cr과 Zn 제거를 위한 전기화학적 공정의 설계

학위논문(석사) - 한국과학기술원 : 화학공학과, 1995.2, [ v, 55 p. ]Treatment of waste water containing chromium and zinc by an electrochemical method was investigated. Chromium can exist as either trivalent or hexavalent compounds in raw waste water. Hexavalent chromium treatment involves reduction to the trivalent form before removal of chromium from the waste water as a hydroxide precipitate. The electrochemical process consists of sacrificial iron electrodes that have direct current applied to the anodes and cathodes to produce ferrous hydroxide. Chromate is reduced from the hexavalent form to the insoluble trivalent state by the ferrous hydroxide. The batch experiment results were assessed in terms of decreasing of chromium and zinc concentration. Several operating variables, such as interval of electrodes, pH, residence time and electrolyte were considered. Optimum operating range for each of these operating variables was experimentally determined. Proper amount of NaOH was added to provide co-precipitation and adsorption conditions which resulted simultaneous removal of chromium and zinc. Using the operating conditions obtained in the batch experiments, a continuous experimental process was designed and test runs were performed. The degree of reaction of chromium and zinc with ferrous ion from iron electrode was shown as a function of residence time and pH when the current density was maintained at a constant value. Simultaneous removal of zinc and chromium was possible by efficiently shifting the equilibrium state and adjusting pH to create conditions for maximum anion adsorption. Chromium was reduced down to undetectable concentration and zinc of concentration was also reduced to less than 1 ppm.한국과학기술원 : 화학공학과