• Title/Summary/Keyword: Chloride process

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A Case Study on the Release Characteristic and Removal Efficiency of Vinyl Chloride in the Poly Vinyl Chloride Extrusion Process (PVC압출공정의 염화비닐 발생특성과 작업환경개선에 관한 사례연구)

  • Park, Dong Uk
    • Journal of Korean Society of Occupational and Environmental Hygiene
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    • v.3 no.1
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    • pp.91-98
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    • 1993
  • This study was carried out to investigate characteristic of vinyl chloride emissioned from poly vinyl chloride extrusion process and to evaluate the efficiency of local exhaust ventilation system. Before local ventilation facility was constructed in poly vinyl chloride extrusion process, the average worker exposure to vinyl chloride was 3.15 ppm, which exceeded Threshold Limit Value of American Conference of Gorvernmental Industrial Hygienists (ACGIH-TLV), 1 ppm. lt is possible that vinyl chloride residues in the poly vinyl chloride resin was released or degased due to extrusion heat. The larger the width of vinyl tube become, the higher worker exposure to vinyl chloride was. It is estimated that vinyl chloride from vinyl chloride resin increased as amount of poly vinyl chloride resin extruded in the extrusion process increased. Canopy hood was an appropriate type for poly vinyl chloride resin extrusion process. This local exhaust ventilation has fan static pressure of 7.65 inch wg($190mmH_2O$, total volumetric flowlate of 4,796 CFM ($135.8m^3$/min) and fan power requirement of 12 hp (8.952 Kw). After this local exhaust ventilation was constructed there, the average concentration of worker exposure to vinyl chloride was reduced to be 0.46 ppm, which was below the Threshold Limit Value, 1 ppm. Also, the removal efficiency rate of vinyl chloride attained by local exhaust ventilation was 85.3%. It was a statistically significant (p<0.01).

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Probabilistic evaluation of chloride ingress process in concrete structures considering environmental characteristics

  • Taisen, Zhao;Yi, Zhang;Kefei, Li;Junjie, Wang
    • Structural Engineering and Mechanics
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    • v.84 no.6
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    • pp.831-849
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    • 2022
  • One of the most prevalent causes of reinforced concrete (RC) structural deterioration is chloride-induced corrosion. This paper aims to provide a comprehensive insight into the environmental effect of RC's chloride ingress process. The first step is to investigate how relative humidity, temperature, and wind influence chloride ingress into concrete. The probability of initiation time of chloride-induced corrosion is predicted using a probabilistic model that considers these aspects. Parametric analysis is conducted on several factors impacting the corrosion process, including the depth of concrete cover, surface chloride concentration, relative humidity, and temperature to expose environmental features. According to the findings, environmental factors such as surface chloride concentration, relative humidity and temperature substantially impact on the time to corrosion initiation. The long- and short-distance impacts are also examined. The meteorological data from the National Meteorological Center of China are collected and used to analyze the environmental characteristics of the chloride ingress issue for structures along China's coastline. Finally, various recommendations are made for improving durability design against chloride attacks.

Effect of Salts on the Formation of $\alpha$-Calcium Sulfate Hemihydrate from by-Product Gypsum of Phosphoric Acid Process under Water Vapor at Atmospheric Pressure (상압 수증기중에서 인산 석고로부터 $\alpha$형 반수석고의 생성에 미치는 염류의 영향)

  • 이구종;최상흘
    • Journal of the Korean Ceramic Society
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    • v.25 no.3
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    • pp.300-306
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    • 1988
  • The catalytic effect of salts on formation of ${\alpha}$-calcium sulfate hemihydrate under water vapor at atmospheric pressure was studied and the formation of q-calcium sulfate hemilydrate from by-product gypsum of phosphoric acid process was investigated. The order of catalytic effect of salts are as follow: Ammonium chloride>Sodium succinate>Calcium chloride>Sodium tartrate>Magnesium chloride The prismatic crystals was formed when ammonium chloride, calcium chloride and magnesium chloride was added, whereas the needle crystals was formed when sodium tartrate was added. Ammonium chlorideis most successful in catalytic effects in formation of ${\alpha}$-calcium sulfate hermihydrate for the by-product gypsum of phosphoric acid process.

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Chloride diffusion study in different types of concrete using finite element method (FEM)

  • Paul, Sajal K.;Chaudhuri, Subrata;Barai, Sudhirkumar V.
    • Advances in concrete construction
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    • v.2 no.1
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    • pp.39-56
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    • 2014
  • Corrosion in RCC structures is one of the most important factors that affects the structure's durability and subsequently causes reduction of serviceability. The most severe cause of this corrosion is chloride attack. Hence, to prevent this to happen proper understanding of the chloride penetration into concrete structures is necessary. In this study, first the mechanism of this chloride attack is understood and various parameters affecting the process are identified. Then an FEM modelling is carried out for the chloride diffusion process. The effects of fly ash and slag on the diffusion coefficient and chloride penetration depth in various mixes of concretes are also analyzed through integrating Virtual RCPT Lab and FEM.

Experimental Study on Deterioration Characteristics under Combined Exposure Conditions of Chlorides and Sulfates (염화물 및 황산염 복합환경 하에서의 열화특성에 관한 실험적 연구)

  • 오병환;인광진;강의영;김지상;서정문
    • Proceedings of the Korea Concrete Institute Conference
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    • 2001.11a
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    • pp.771-776
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    • 2001
  • Test results on the deterioration process of concrete under single and combined attacks of chloride penetration have been obtained. After test period of 52 weeks, it is found that the internally penetrated chloride ion contents are less in the single attacks of chloride than the combined attacks of chloride and sulfate. Both the diffusion coefficients and surface chloride concentration derived form the chloride profiles showed a time dependence. Also the performance of fly ash-blended cements was observed to be better than plain cements in retarding chloride attack. However it should be needed that improved chloride diffusion model for the combined deterioration process.

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Two Dimensional Chloride Ion Diffusion in Reinforced Concrete Structures for Railway

  • Kang, Bo-Soon;Shim, Hyung-Seop
    • International Journal of Railway
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    • v.4 no.4
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    • pp.86-92
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    • 2011
  • Chloride ion diffusion at the corner of rectangular-shaped concrete structures is presented. At the corner of rectangular-shaped concrete, chloride ion diffusion is in two-dimensional process. Chloride ions accumulate from two orthogonal directions, so that corrosion-free life of concrete structures is significantly reduced. A numerical procedure based on finite element method is used to solve the two-dimensional diffusion process. Orthotropic property of diffusion coefficient of concrete is considered and chloride ion profile obtained from numerical analysis is used to produce transformed diffusion coefficient. Comparisons of experimental data are also carried out to show the reliability of proposed numerical analysis. As a result of two-dimensional chloride diffusion, corrosion-free life of concrete structure for railway is estimated using probability of corrosion initiation. In addition, monographs that produces transformed diffusion coefficient and corrosion-free life of concrete structure are made for maintenance purpose.

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Simple approach to calculate chloride diffusivity of concrete considering carbonation

  • Yoon, In-Seok
    • Computers and Concrete
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    • v.6 no.1
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    • pp.1-18
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    • 2009
  • Chloride diffusivity of concrete is a crucial material parameter for service life determination and durability designing of marine concrete. Many research works on this issue have been conducted, varying from empirical solutions obtained experimentally to image analysis, based on multi-scale modeling. One of the simple approaches is to express the chloride diffusivity of concrete by a multi-factor function, however, the influences of various factors on the chloride diffusivity are ambiguous. Furthermore, the majority of these research works have not dealt with the carbonation process of concrete, although this process affects the chloride diffusivity of concrete significantly. The purpose of this study is to establish a simple approach to calculate the chloride diffusivity of (non)carbonated concrete. The chloride diffusivity of concrete should be defined, based on engineering and scientific knowledge of cement and concrete materials. In this paper, a lot of parameters affecting the chloride diffusivity, such as the diffusivity in pore solution, tortuosity, micro-structural properties of hardened cement paste, volumetric portion of aggregate, are taken into consideration in the calculation of the chloride diffusivity of noncarbonated concrete. For carbonated concrete, reduced porosity due to carbonation is calculated and used for calculating the chloride diffusivity. The results are compared with experimental data and previous research works.

SEPARATION OF STRONTIUM AND CESIUM FROM TERNARY AND QUATERNARY LITHIUM CHLORIDE-POTASSIUM CHLORIDE SALTS VIA MELT CRYSTALLIZATION

  • WILLIAMS, AMMON N.;PACK, MICHAEL;PHONGIKAROON, SUPATHORN
    • Nuclear Engineering and Technology
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    • v.47 no.7
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    • pp.867-874
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    • 2015
  • Separation of cesium chloride (CsCl) and strontium chloride ($SrCl_2$) from the lithium chloride-potassium chloride (LiCl-KCl) salt was studied using a melt crystallization process similar to the reverse vertical Bridgeman growth technique. A ternary $SrCl_2-LiCl-KCl$ salt was explored at similar growth rates (1.8-5 mm/h) and compared with CsCl ternary results to identify similarities. Quaternary experiments were also conducted and compared with the ternary cases to identify trends and possible limitations to the separations process. In the ternary case, as much as 68% of the total salt could be recycled per batch process. In the quaternary experiments, separation of Cs and Sr was nearly identical at the slower rates; however, as the growth rate increased, $SrCl_2$ separated more easily than CsCl. The quaternary results show less separation and rate dependence than in both ternary cases. As an estimated result, only 51% of the total salt could be recycled per batch. Furthermore, two models have been explored to further understand the growth process and separation. A comparison of the experimental and modeling results reveals that the nonmixed model fits reasonably well with the ternary and quaternary data sets. A dimensional analysis was performed and a correlation was identified to semipredict the segregation coefficient.

Experimental Study of Chlorides Ion Diffusion Characteristics under Combined Condition of Chlorides and Sulfates (염해 및 황산염의 복합작용에 따른 염소이온 확산특성의 실험적 연구)

  • 오병환;김선우;정상화;서정문
    • Proceedings of the Korea Concrete Institute Conference
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    • 2000.10a
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    • pp.413-418
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    • 2000
  • The test results on the deterioration process of concrete under single and combined action of chloride penetration have been obtained. Within the test period of 15 weeks, it is seen that the internally penetrated chloride ion contents are slightly less in the combined action of NaCI and $Na_2SO_4$ than the single action of NaCI. Also the theoretical prediction of chloride penetration based on measured diffusion coefficient agress well with the test data of single deterioration process but disagress with that of combined process. Therefore it should be needed that improved chloride diffusion model for the combined deterioration process.

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Influence of flexural loading on chloride ingress in concrete subjected to cyclic drying-wetting condition

  • Ye, Hailong;Fu, Chuanqing;Jin, Nanguo;Jin, Xianyu
    • Computers and Concrete
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    • v.15 no.2
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    • pp.183-198
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    • 2015
  • Chloride ingress implies a complex interaction between physical and chemical process, in which heat, moisture and chloride ions transport through concrete cover. Meanwhile, reinforced concrete structure itself undergoes evolution due to variation in temperature, relative humidity and creep effects, which can potentially change the deformation and trigger some micro-cracks in concrete. In addition, all of these process show time-dependent performance with complex interaction between structures and environments. In the present work, a time-dependent behavior of chloride transport in reinforced concrete beam subjected to flexural load is proposed based on the well-known section fiber model. The strain state varies because of stress redistribution caused by the interaction between environment and structure, mainly dominated by thermal stresses and shrinkage stress and creep. Finally, in order to clear the influence of strain state on the chloride diffusivity, experiment test were carried out and a power function used to describe this influence is proposed.