• Fire Science and Engineering
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• v.30 no.6
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• pp.99-104
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• 2016

In animal and plant facilities, dust samples were collected from cattle sheds, pigsties and hen-houses, which have high proportion of electrical fires. The samples were diluted in distilled water and water resistivity was measured. Current measurements and tracking reappearance experiments were conducted using distilled water with dust samples. The analysis results were obtained to track the fire risks according to the dust resistivity. The highest value was the dust from cattle sheds followed in order by the dust of pigsties and hen-houses. In experiments measuring the temperature change and RMS current, the lower resistivity of water showed a significant trend of temperature and high amperage. In the tracking reappearance experiment with the lower resistivity water, the tracking speed was fast and the ignition time was shortened. This study investigated why each dust resistivity shows different results.

• Journal of Mechanical Science and Technology
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• v.15 no.5
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• pp.630-638
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• 2001

The electrical resistivity of sinter dusts generated from the steel industry and coal fly ash from the coal power plant has been investigated using the high voltage conductivity cell based on JIS B 9915 as a function of temperature and water content. Dust characterization such as the chemical composition, size distribution, atomic concentration, and surface structure has been conducted. Major constituents of sinter dusts were Fe$_2$O$_3$(40∼74.5%), CaO (6.4∼8.2%), SiO$_2$(4.1∼6.0%), and unburned carbon (7.0∼14.7%), while the coal fly ash consisted of mainly SiO$_2$(51.4%), Al$_2$O$_3$(24.1%), and Fe$_2$O$_3$(10.5%). Size distributions of the sinter dusts were bi-modal in shape and the mass median diameters (MMD) were in the range of 24.7∼137㎛, whereas the coal fly ash also displayed bi-modal distribution and the MMD of the coal fly ash was 35.71㎛. Factors affecting resistivity of dusts were chemical composition, moisture content, particle size, gas temperature, and surface structure of dust. The resistivity of sinter dusts was so high as 10(sup)15 ohm$.$cm at 150$\^{C}$ that sinter dust would not precipitate well. The resistivity of the coal fly ash was measured 1012 ohm$.$cm at about 150$\^{C}$. Increased water contents of the ambient air lowered the dust resistivity because current conduction was more activated for absorption of water vapor on the surface layer of the dust.

• Advances in concrete construction
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• v.2 no.3
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• pp.163-176
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• 2014

Essentially, when electrical current flows easily in concrete that has large pores filled with highly connective pore water, this is an indication of a low resistivity concrete. In concrete, the flow of current between anodic and cathodic sites on a steel reinforcing bar surface is regulated by the concrete electrical resistance. Therefore, deterioration of any existing reinforced concrete structure due to corrosion of reinforcement steel bar is governed, to some extent, by resistivity of concrete. Resistivity of concrete can be improved by using SCMs and thus increases the concrete electrical resistance and the ability of concrete to resist chloride ingress and/or oxygen penetration resulting in prolonging the onset of corrosion. After depassivation it may slow down the corrosion rate of the steel bar. This indicates the need for further study of the effect of electric arc furnace dust (EAFD) addition on the concrete resistivity. In this study, concrete specimens rather than mortars were cast with different additions of EAFD to verify the electrochemical results obtained and to try to understand the role of EAFD addition in influencing the corrosion behaviour of reinforcing steel bar embedded in concrete and its relation to the resistivity of concrete. The results of these investigations indicated that the corrosion resistance of steel bars embedded in concrete containing EAFD was improved, which may link to the high resistivity found in EAFD-concrete. In this paper, potential measurements, corrosion rates, gravimetric corrosion weight results and resistivity measurements will be presented and their relationships will also be discussed in details.

• Journal of the Korean Society of Safety
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• v.17 no.4
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• pp.25-30
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• 2002

This paper demonstrates the effects of dust electrical resistivity on electrostatic precipitability. The effects of gas temperature, velocity and humidity on the collection efficency were considered by used of coal fly ashes from fluidized bed combustion boiler. The experiments for collection efficiency were carried out in the pilot plant. The ashes which have non-spherical geometry and high electrical resistivity were used. Electrical resistivity is an important property for the collection efficiency in the electrostatic precipitators. Fly ash resistivity as a function of temperature up $350{\circ}C$ and water concentration(up to 15%) has been experimentally investigated using the resistivity test equipment consisted of the movable electrode, dust cup, and furnace. As the resistivity of fly ash in the operating temperature($150{\circ}C$) of an electrostatic precipitator was measured higher than $1010{\Omega}{\cdot}$cm, flue gas conditioning in the electrostatic precipitator to reduce the resistivity of fly ash is required.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.24 no.4
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• pp.526-532
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• 2000

Recent studies have been directed toward obtaining a better understanding of the application of electrostatic precipitators to collect fly ash particles produced in a coal-fired power plant. Electrical resistivity can be described as the resistance of the collected dust layer to the flow of electrical current and is an important property for the collection efficiency in the electrostatic precipitator. In this paper, fly ash resistivity as a function of temperature up to $450^{\circ}C$ has been experimentally investigated using the resistivity meter consisted of the movable electrode, dust cup, and furnace. Resistivity was found to increase with increased temperature up to $200^{\circ}C$ due to the reduction of water concentration and then gradually decrease with increased temperature due to the activation of electrons. As the resistivity of fly ash in the flue gas temperature of $150^{\circ}C$ was measured >$10^{10}$ ohm cm, the efficiency of fly ash removal in the electrostatic precipitator might be expected to be low due to back-corona phenomenon. Flue gas conditioning in the electrostatic precipitator to reduce the resistivity of fly ash as required.

• Proceedings of the SAREK Conference
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• 2006.06a
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• pp.448-453
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• 2006

Electrical resistivity is an important property for the collection efficiency in the electrostatic precipitator. In this paper, electrical resistivities of tobacco dusts, yellow sand dusts and pine pollens are measured using a high voltage conductivity cell based on JIS B 9915. The resistivities of three kinds of indoor dusts are about $1{\times}10^7\;{\Omega}{\cdot}cm^2$ in the normal range and dust collection efficiency using an electrostatic precipitator at to face velocity of 1.0 m/s shows over 99% for the three kinds of indoor dusts.

• Computers and Concrete
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• v.23 no.3
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• pp.189-201
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• 2019

Recent advances in the concrete technology are aiding in minimizing the use of conventional materials by substituting by-products of various industries and energy sources. A large amount of stone waste i.e., dust and slurry form both are being originated during natural stone processing and causing deadily effects on the environment. The disposal problem of stone waste can be resolved effectively by using waste in construction industries. In present work, Kota stone slurry powder, as a substitution of cement was used along with accelerators namely calcium nitrate and triethanolamine as additives, to study their impact on various properties of the concrete mixtures. Kota stone slurry powder (7.5%), calcium nitrate (1%) and triethanolamine (0.05%) were used separately as well in combination in different concrete mixtures. Mechanical Strength, modulus of elasticity and electrical resistivity of concrete specimens of different mix proportions under water curing were studied experimentally. The durability properties in terms of strength and electrical resistivity against sulphate and chloride solution attack at various curing ages were also studied experimentally. Results showed that accelerators and Kota stone slurry powder separately enhanced the mechanical strength and electrical resistivity; but, their combination decreased strength at all curing ages. The durability of concrete specimens was also affected under the exposure to chemical attack too. Kota stone slurry powder found to be the most effective material among all materials. Material characterization was also done to study the microstructural properties.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.49 no.10
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• pp.570-576
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• 2000

The discharge and the collection efficiency characteristics of an electrostatic precipitator have been studied under various operating conditions. The specific resistivity of pulverized coal dust was about 1013∼1014[${\Omega}{\cdot}cm$] and reached the maximum value of 6${\times}$1013[${\Omega}{\cdot}cm$] at 150[$^{\circ}C$]. Back corona has been occurred as dust contents and gas temperature increase. In the case of back corona occurrence, collection effciency decreased rapidly. This problem has been solved by increasing moisture contents. Experimental results showed that collection efficiency of the full wave voltage was higher than that of the pulse wave voltage. The modification parameter k of the collection efficiency equation was about 0.42.

• Proceedings of the Korea Concrete Institute Conference
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• 2000.10b
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• pp.933-938
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• 2000

Concrete has been used for many years as a composite material that has excellent mechanical properties and durability for construction. However, concrete is a poor electrical conductor, especially under dry conditions. Concrete that is excellent in both mechanical and electrical conductivity properties may have important applications in the electrical, electronic, military and construction industry(e.g. for de-icing road from snow). The purpose of this investigation is to improve the electrical conductive of cement mortar preparared with coke dust, graphite, carbon black and carbon fiber as filler. From the test result, as the content of electrically conductive material increased, fluidity and strength decreased but resistivity decreased. The resistivity of electrical conductive cement mortar is effect by water/cement, and aggregate. Cement mortar containing carbon fiber has the best electrical properties considering strength. From this study, it is enough to assure the use of carbon fiber, carbon black and graphite as a conductive filler for electrical conductive cement mortar.

• Journal of the Korean Applied Science and Technology
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• v.31 no.4
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• pp.679-687
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• 2014

In this study, a new paint which is able to resist the cavitation erosion is tried to be developed by using urethane added with nano particles such as multi-wall and single-wall carbon nano tube and spherical and fiber type graphite. The new paint synthesized was characterized with physical properties and resistivity to cavitation erosion($t_{50}$). Among nano particles, fiber type graphite($t_{50}$ 292min) showed high hardness and wear resistance compared with spherical type($t_{50}$ 182min). For carbon nano tube, single-wall type($t_{50}$ 286min) was higher than multi-wall type in wear resistance. Fiber-type graphite was the best nano-particle for paint with resistivity to cavitation erosion. In the application test of paint, the manually painted sample showed surface with smooth but the surface of sample prepared with spray was not smooth. During spray, dust was fixed on the surface.