• Applied Chemistry for Engineering
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• v.16 no.3
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• pp.337-341
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• 2005

This paper reports the study on coking rate and carbon formation route as a function of reaction temperature using the Ni catalysts in the $CO_2$ reforming of methane. In this paper, carbon deposition on catalysts and its kinetics during reforming reaction were studied by using a thermogravimetric analyzer. Kinetic studies show that reaction orders of carbon formation obtained 1.33 ($CH_4$) and -0.52 ($CO_2$) by experiments on partial pressure of reactant gas, respectively. On the basis of model equation, the kinetic parameters for the coking reaction at different temperatures indicated that methane decomposition dominated carbon formation at lower temperatures ($<600^{\circ}C$), while $CH_4$decomposition and Boudouard reactions become significant for coking in the temperature range of $600{\sim}700^{\circ}C$.

• Carbon letters
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• v.28
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• pp.38-46
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• 2018

Modified pitch A (MPA) and modified pitch B (MPB) were prepared by oxidative polymerization and thermal polycondensation reaction with refined pitch as the raw material, respectively. The toluene soluble components (TS-1 and TS-2) were obtained by solvent extraction from MPA and MPB, separately. The Flynn-Wall-Ozawa method and Kissinger-Akahira-Sunose method were used to calculate the pyrolysis activation energy of TS. The Satava-Sestak method was used to investigate the pyrolysis kinetic parameters of TS. Moreover, the optical microstructure of the thermal conversion products (TS-1-P and TS-2-P) by calcination shows that TS-1-P has more contents of mosaic structure and lower contents of fine fiber structure than TS-2-P. The research result obtained by a combination of X-ray diffraction and the curve-fitting method revealed that the ratios of ordered carbon crystallite (Ig) in TS-1-P and TS-2-P were 0.3793 and 0.4417, respectively. The distributions of carbon crystallite on TS-1-P and TS-2-P were calculated by Raman spectrum and curve-fitting analysis. They show that the thermal conversion product of TS-2 has a better graphite crystallite structure than TS-1.

• Transactions of the Korean hydrogen and new energy society
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• v.26 no.5
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• pp.445-452
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• 2015

A tubular packed bed reactor for the steam-$CO_2$ combined reforming of natural gas to produce the synthesis gas of a target $H_2/CO$ ratio 2.0 was simulated. The effects of the reactor dimension, the feed gas composition, and the gas feeding temperature upon the possibility of coke formation across the catalyst bed were investigated. For this purpose, 2-dimensional heterogeneous reactor model was used to determine the local gas concentrations and temperatures over the catalyst bed. The thermodynamic potential distribution of coke formation was determined by comparing the extent of reaction with the equilibrium constant given by the reaction, $CH_4+2CO{\Leftrightarrow}3C+2H_2O$. The simulation showed that catalysts packed in the central region nearer the entrance of the reactor were more prone to coking because of the regional characteristics of lower temperature, lower concentration of $H_2O$, and higher concentration of CO. With the higher feeding temperature, the feed gas composition of the increased $H_2O$ and correspondingly decreased $CO_2$, or the decrease in the reactor diameter, the volume fraction of the catalyst bed subsequent to coking could be diminished. Throughout the simulation, reactor dimension and reaction condition for coking-free operation were suggested.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2006.05a
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• pp.100-109
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• 2006

In the regeneratively cooled combustion chambers using hydrocarbon fuels, coking occurs as the wall temperature increases which generates compounds deposition on the wall. This phenomenon reduces cooling capability of the coolant, finally it can cause damage to combustor by overheating of chamber wall. In this paper electrical heating equipment which is used for the coking experiments and the test results are introduced. The compatibilities of copper alloy with let A-1 were assessed at each condition based on the test results.

• International Journal of Advanced Culture Technology
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• v.3 no.1
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• pp.31-38
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• 2015

Coking accumulations via dry methane reforming (DMR) over 10NAM monolithic catalyst and pelletized catalyst was investigated. 10NAM catalyst was synthesized and coated on a wall of monolithic reactor. Pelletized catalyst of 10NAM was also prepared for the comparison. Consequently, catalyst was characterized by BET, $H_2-TPR$ and $H_2-TPD$. The catalytic reaction was undergone at $600^{\circ}C$ under atmospheric pressure and $CH_4$ to $CO_2$ reactant ratio of 1:2. The coking formation over spent catalyst was then carried out in the hydrogen flow using temperature programmed technique (TPH). According to the results, DMR over 10NAM monolithic catalyst exhibits a minimized coking formation comparing to the use of pelletized catalyst. This could be attributed to a prominent heat transfer efficiency of the monolithic catalyst.

• Korea Trade Review
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• v.44 no.2
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• pp.127-141
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• 2019

In this study, the relationship between Baltic Dry Index(BDI) and maritime trade volume in the dry cargo market was verified using the vector autoregressive (VAR) model. Data was analyzed from 1992 to 2018 for iron ore, steam coal, coking coal, grain, and minor bulks of maritime trade volume and BDI. Granger causality analysis showed that the BDI affects the trade volume of coking coal and minor bulks but the trade volume of iron ore, steam coal and grain do not correlate with the BDI freight index. Impulse response analysis showed that the shock of BDI had the greatest impact on coking coal at the two years lag and the impact was negligible at the ten years lag. In addition, the shock of BDI on minor cargoes was strongest at the three years lag, and were negligible at the ten years lag. This study examined the relationship between maritime trade volume and BDI in the dry bulk shipping market in which uncertainty is high. As a result of this study, there is an economic aspect of sustainability that has helped the risk management of shipping companies. In addition, it is significant from an academic point of view that the long-term relationship between the two time series was analyzed through the causality test between variables. However, it is necessary to develop a forecasting model that will help decision makers in maritime markets using more sophisticated methods such as the Bayesian VAR model.

• Journal of the Korean Society of Propulsion Engineers
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• v.24 no.3
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• pp.81-124
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• 2020

In liquid oxygen/kerosene liquid rocket engines, kerosene is not only a propellant but also plays a role as a coolant to protect the combustion chamber wall from 3,000 K or more combustion gas. Since kerosene is exposed to high temperature passing through cooling channels, it may undergo heat-related chemical reactions leading to precipitation of carbon-rich solids. Such kerosene's thermal and fluidic characteristic test data are essential for the regeneratively cooled combustion chamber design. In this paper, we investigated foreign studies related to regenerative cooling channel and kerosene. Starting with general information on hydrocarbon fuels including kerosene, we attempted to systematically organize sedimentary phenomena on cooling channel walls, their causes/research results, coking test equipments/prevention methods, etc.

• Journal of the Korea Organic Resources Recycling Association
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• v.18 no.4
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• pp.38-44
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• 2010

Foundry sands are made up of silica and some coking agents, such as bentonite or resin, and used as templates for the production of various casting products. Foundry sands, which are repeatedly used, were finally transformed into the waste materials by heat, losing their proper functions. The used foundry sands have been treated as general wastes according to the contents of coking agents used. Silica, however, can be recycled through the proper treatment due to its physical property not to changed by heat. In this study, we have identified and investigated at the occurrence, treatment and recycling status of the used foundry sands, as well as for the regime and inhibitory factors of the recycling of them in domestic and foreign cases.

• Tribology and Lubricants
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• v.13 no.4
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• pp.33-39
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• 1997

In order to establish a new temperature criterion to prevent the pistons from ring sticking due to deposit formation, bench test and engine test were performed. The effects of oil degradation and temperature on deposit formation was studied by a modified panel coking test. Oil degradation was analyzed by FTIR. Oil oxidation and nitration were selected as a factors to evaluate oil degradation. Bench test results show that oil oxidation is more effective to the deposit formation than oil nitration. And the temperature increase accelerates deposit formation and deposit formation increase rapidly above 26$0^{\circ}C$. Especially, in case of degraded oil, the deposit formation increases so rapidly that ring sticking can occur. The effect of piston temperature on the deposit formation was confirmed by engine test.

• Proceedings of the KWS Conference
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• 2002.10a
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• pp.675-680
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• 2002

Cracking and bulging in welded and internally lined pressure vessels that work in thermal-mechanical cycling service have been well known problems in the petrochemical, power and nuclear industries. However, published literature and industry surveys show that similar problems have been occurring during the last 50 years. A better understanding of the causes of cracking and bulging causes is needed to improve the reliability of these pressure vessels. This study attempts to add information required for increasing the knowledge and fundamental understanding required. Typical examples of this problem are the coke drums in the delayed coking units refinery process. This case was selected for experimental work, field study and results comparison. Delayed coking units are among the refinery units that have higher economical yields. To shut down these units represents a high negative economical impact in refinery operations. Also, the maintenance costs associated with repairs are commonly very high. Cracking and bulging occurrences in the coke drums, most often at the weld areas, characterize the history of the operation of delayed coking units. To design and operate more robust coke drums with fewer problems, an improved metallurgical understanding of the cracking and bulging mechanisms is required. A methodology that is based field experience revision and metallurgical analyses for the screening of the most important variables, and subsequent finite element analyses to verify hypotheses and to rank the variables according to their impact on the coke drum lives has been developed. This indicated approach provides useful information for increasing coke drum reliability. The results of this work not only order the most important variables according to their impact in the life of the vessels, but also permit estimation of the life spans of coke drums. In conclusion, the current work shows that coke drums may fail as a combination of thermal fatigue and other degradation mechanisms such as: corrosion at high and low temperatures, detrimental metallurgical transformations and plastic deformation. It was also found that FEA is a very valuable tool for understanding cracking and bulging mechanisms in these services and for ranking the design, fabrication, operation and maintenance variables that affect coke drum reliability.